Hinsberg Test for Amine

Distinction between primary, secondary and tertiary amine Using Hinsberg  reagent

Three classes of amines are distinguished by Hinsberg reagent test. The Hinsberg reagent is benzene sulphonyl chloride (C6H5SO2Cl).

1. Reaction of Hinsberg reagent with Primary amine

A primary amine forms a precipitate of N-alkyl benzene sulphonamide with Hinsberg reagent. This precipitate is soluble in alkali.

RNH2 (primary amine)  +  C6H5SO2Cl (Hinsberg reagent) ------------>  R-NH-SO2-C6H5  ------(NaOH)---> R-N-Na+-SO2C6H5 (soluble)

2. Reaction of Hinsberg reagent with secondary amine

 Secondary amine reacts with Hinsberg reagent to form a precipitate N,N-dialkyl benzene sulphonamide. But this precipitate is insoluble in alkali.

R2NH (secondary amine)  +  C6H5SO2Cl (Hinsberg reagent) ------------> R2NSO2C6H5 (precipitate)  -----(NaOH)---> insoluble (no reaction)

2. Reaction of Hinsberg reagent with Tertiary amine

Tertiary amines do not react with Hinsberg reagent,

R3N (Tertiary amine)  +  C6H5SO2Cl (Hinsberg reagent) ------------>No reaction

Hinsberg reagent can also be used for the separation of primary, secondary and tertiary amine from a mixture.

General Knowledge Questions: Chemistry

GK Chemistry Questions and answer about Elements

Some frequently asked Chemistry gk questions about elements

Chemistry GK >> 1. Hydrogen

1. Which is the most abundant element in the Universe ?
Answer: Hydrogen

2. Which is the atom without Neutron ?
Answer: Hydrogen

3. Who discovered Hydrogen ?
Answer: Henry Cavendish

4. Who named Hydrogen ?
Answer: Lavoisier

5. Which isotope of Hydrogen has Radio Active nature ?
Answer: Tritium

6. Which gas is used to make Vanaspathi ?
Answer: Hydrogen

7. Which is the lightest element ?
Answer: Hydrogen

8. Which is the element common to all Acid ?
Answer: Hydrogen

Chemistry GK >> 2. Helium 

1. Which is the second most abundant element in the universe ?
Answer: Helium

2. Which gas is used to for filling air ships and observation balloons ?
Answer: Helium

3. Who discovered Helium ?
Answer: William Ramsay

4. Which is the lightest Noble gas ?
Answer:  Helium

* Chemistry GK >> 3. Lithium

1. Which metal has least density ?
Answer: Lithium

2. Which metal is kept in wax ?
Answer: Lithium

* Chemistry GK >> 4. Carbon

1. Who discovered Carbon dioxide ?
Answer: Joseph black

2. Who discovered Carbon Monoxide ?
Answer: Joseph Priestly

3. Solid form of Carbon dioxide is known as ?
Answer: Dry Ice

4. What is water gas ?
Answer: Mixture of carbon monoxide and hydrogen

5. What is Producer gas ?
Answer:  Mixture of carbon monoxide and Nitrogen

* newly updated
General knowledge chemistry Questions about more element will be added soon..

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 For possible chemistry gk questions visit Chemical name and GK questions

 If you know more questions about those element please add it as comment, help others.

Application of Adsorption

Industrial Application of Adsorption Process

1. Activated charcoal is used to remove bad odours inside refrigerator and to deodourise tap water in water purifier. It is also used in gas masks to adsorb poisonous gases in the atmosphere.

2. In sugar industry animal charcoal is used to decolourise raw sugar solution obtained from sugar cane.

3. In chromatography, suitable adsorbents are used. They selectively adsorb certain substance from solution. Adsorption chromatography is used for detection and separation of mixtures.

4. In dehumidifier, silica gel is used as adsorbent.

5. Activated charcoal is  used to maintain vacuum in laboratory vessels such as Dewar flask.

6. Heterogeneous catalysis  mostly operate through adsorption of reactant molecules.

7. Softening of water using ion exchange resin is based on selective adsorption of ions which cause hardness.

8. In mordant dyeing, mordants adsorb colour.

9. Ferric hydroxide can adsorb arsenic ions and hence it is used as antidote against arsenic poisoning.

Adsorption Isobar

Adsorption Isobar : Effect of temperature

Most of the adsorptions are exothermic reactions, Hence adsorption generally depend on temperature. Exothermic reactions are mostly spontaneous at low temperature. Hence the extent of adsorption decreases with increase of temperature at constant pressure. A plot of extent of adsorption verses temperature at constant pressure is known as adsorption Isobar.

Factors affecting adsorption

Factors affecting adsorption: Pressure of Gas

Adsorption and desorption are reversible process and take place simultaneously leading to equilibrium state.

Adsorbent + gas  <========> Adsorbent gas

In the forward direction, during adsorption, volume decreases since gases are adsorbed to the surface. Hence applying Le-Chatelier principle, we can predict effect of pressure. At high pressure, the system has a tendency to decrease volume and shifts towards forward direction, ie , more adsorption take place. Now we can conclude that extent of adsorption (x/m) increases with increase in pressure. Where x= number of the moles of gas adsorbed and m = mass of adsorbent, at equilibrium. Variation of  x/m with pressure can be experimentally studied and can be plotted as a graph at constant temperature. Such graphs obtained by plotting (x/m) against (p) at constant temperature are called, adsorption isotherm.

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Factors influencing adsorption process

Specific area of adsorbent affects adsorption of gases on solids

The surface area of an adsorbent available for adsorption is known as specific area of adsorbent. Depending on the nature of surface, impurity at the surface etc, specific area of adsorbent changes. Rough surface can adsorb more, due to greater available surface area. Similarly solids can adsorb more when powdered. When powdered, surface area increases. Hence porous and finely divide forms of adsorbent have greater adsorption power.

Activation of adsorbent

We can increase the activity of an adsorbent using different methods. Cleaning surface, making rough surface, powdering etc are some of these method.

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Factors affecting adsorption of gases on solids

Important Factors affecting adsorption of gases are

1. Nature of gas.
2. Nature of adsorbent.
3. Specific area of adsorbent.
4. Activation of the adsorbent.
5. Pressure of the gas.
6. Temperature

1. Nature of gas

Adsorption can be either physisorption or chemisorption. Chemical adsorption is highly specific, hence only a particular adsorbent can adsorb a gas. For example, Nitrogen is adsorbed by Iron. Adsorption of hydrogen by nickel or platinum.

But physisorption is not specific. In such cases it is observed that easily liquefiable gases are more adsorbed than permanent gases like He, N2, O2, H2 etc. It is due to the reason that HCl, SO2, CH4, NH3, SO3 etc are more adsorbed. In case of easily liquefiable gases, van der Waals  force or molecular forces are more predominant, and hence physisorption becomes more significant.

2. Nature of adsorbent

The extent of adsorption depends on nature of the adsorbent. Charcoal and silica gel are good adsorbent for gases and moisture respectively. Similarly H2 is strongly adsorbed by Ni.

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Physisorption and Chemisorption

Physisorption and Chemisorption definition

In adsorbed state the adsorbate is held on the surface of adsorbent by attractive forces (bond). Depending on the nature of attractive forces, adsorption can be of two types - physical adsorption (Physisorption) and chemical adsorption (Chemisorption). In chemisorption there is a strong chemical bond.

During adsorption, a new bond is formed between adsorbent and adsorbate. Therefore adsorptions are generally exothermic (▵H = -ve). But entropy and free energy decreases during adsorption.

Enthalpy change during adsorption process are called enthalpy of adsorption. It is defined as the heat evolved at constant pressure, when one mole of an adsorbate is adsorbed on the surface of adsorbent. For physical adsorption and chemical adsorption, its values ranges in the order of -20KJ/mol and 200kjmol-1. Difference between physisorption and chemisorption are given below.

Comparison Between Physisorption and Chemisorption

1. In physisorption adsorbate is held on the surface of  adsorbent by van der Waals force.

In chemisorption molecules of adsorbate and adsorbent are held by chemical bonds.

2. In Physisorption enthalpy of adsorption is comparatively low. ie, in the order of 20 kjmol-1.

 In Chemisorption enthalpy of adsorption is high. ie, in the order of 200 kjmol-1.

3.  Physisorption is reversible.

Chemisorption is irreversible.

4. Physisorption is not specific. ie, all gases are adsorbed by an adsorbent.

Chemisorption is highly specific.

5. In physisorption multi molecular layer of adsorbate occurs at the surface.

Chemisorption forms only unimolecular layer.

6. Physisorption usually takes place at low temperature and the extent of adsorption decreases with increase of temperature.

Chemisorption takes place at relatively higher temperature

7. In physisorption easily liquefiable gases are more adsorbed. For example NH3, HCl etc are more adsorbed than permanent gases like He, O2, N2 etc.

 In Chemisorption there is no such correlation.

Importance of Stereochemistry

Stereo chemistry Importance 

Stereochemistry is an important aspect of carbon compounds. It is prevalent in the whole universe. The human body is structurally chiral with the heart lying to the left and the liver to the right in the body. Many plants show chirality which help them to wind around supporting structures. Most of the molecules found in animals and plants are chiral and usually only one form of chiral molecules occur in a species. All the naturally occurring amino acids have L configuration. The synthesized D-proteins made from D aminoacids are some what resistant to break down by protein digesting enzymes.All naturally occurring sugars are of D-configuration. The enzyme, yeast can specifically ferment D-glucose and not its L-form.

Stereo chemistry also plays an important role in deciding the physiological properties of compounds. (-) Nicotine is much more toxic than (+) Nicotine. (+) Adrenaline is very active in constriction of blood vessels than (-) Adrenaline.

Chirality is crucial for the effect of drugs. In many cases only one enantiomer is found to have the desired effect while the other isomer may be totally inactive or has an opposite effect. (-) Thyroxine, an amino acid of thyroid gland speeds up metabolic processes and causes nervousness and loss of weight. But (+) Thyroxin has none of these effects but is used to lower the cholesterol levels.

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Resolution of racemic mixture (dextro and laevo)

Separation of Dextro and Laevo components

The synthesis of optically active compounds in the laboratory usually results in racemic mixture. The d and l forms can be separated from the racemic mixture. The separation of a racemic mixture in to dextro and laevo components is termed resolution. Due to identical physical properties of optical isomers their separation cannot be effected by simple physical methods. Usual methods which have been used for resolving racemic compounds are Mechanical Separation, Biochemical separation and by means of salt formation.

Methods of separation of a racemic mixture in to dextro and laevo components

1. Mechanical Separation

When the two varieties of isomers form well defined crystals they can be separated by hand picking. The crystals of Sodium ammonium racemate can be separated by this method.

2.Biochemical Separation

In this method certain micro organism such as mould, bacteria or fungi when allowed grow in a solution of racemic mixture destroy one of the optical isomers at a much quicker rate than the other due to selective assimilation. When penicillium glaucum is allowed to grow in a solution of ammonium tartrate, it destroys the dextro isomer leaving the laevo isomer.

3. By means of Salt Formation

This is an effective method for resolution. Here the isomers of racemic mixture are converted to their salts with an optically active acid or base. The two salts obtained often differ in their solubilities  and can be sseparated by fractional crystallisation. The salts on treatment with acid or base regenerate the optically active reagent.

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Optical Isomerism

Optical Isomers Definition

Optical isomerism arises due to chirality or asymmetry of the molecule. Optical isomers resemble one another in chemical properties and most of their physical properties but differ in their behavior towards polarized light. The isomer, which rotate the plane of polarized light clockwise is called dextro rotatory isomer (d - isomer) and the one which rotate the plane of polarized light anticlockwise is called laevo rotatory isomer (l - Isomer).

The necessary condition for a molecule to be optically active is asymmetry or chirality of the molecule. Chirality is not just the presence of the asymmetric carbon atom but asymmetry of the molecule as a whole. Most of the chiral molecule contains at least one asymmetric carbon atom (Chiral Carbon atom). Still, there are some organic molecules which exhibit optical isomerism with out having chiral carbon (example: Substituted biphenyls). Some of the organic molecules are optically inactive even though they contain chiral carbon. This is due to internal compensation.

Examples of Optical Isomerism

Optical Isomers of Tartaric acid (HOOC-CHOH-CHOH-COOH)

Optical Isomers of lactic acid

Example of optical Isomer : Tartaric acid

Optical Isomers of Tartaric acid (HOOC-CHOH-CHOH-COOH)

Two chiral carbon atoms are present in tartaric acid. The difference in spatial arrangements of various groups in tartaric acid results in d-tartaric acid, l-tartaric acid and an active form known as meso form. In addition to these, racemic modification, another inactive form also exist.

Dextro tartaric acid rotates the plane of polarization of light to right. The rotation due to upper half is strengthened by the rotation of lower half. Laevo tartaric acid is a mirror image of d-form, which rotate the palne of polarization to left.

Racemic tartaric acid is an equimolar mixture of d and l -isomers. It is optically inactive due to external compensation, it can be resolved into d and l forms.

Meso tartaric acid is an inactive variety and the rotation of upper half is compensated by the rotation due to lower half. It cannot be resolved into active constituents. It is therefore inactive due to internal compensation. Mesotartaric acid possess a plane of symmetry.

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Optical Isomers Example: lactic acid

Optical Isomers of lactic acid

In lactic acid CH3 - CHOH - COOH, second carbon is chiral.

There are two optically active isomers of Lactic acid: d-lactic acid and l-lactic acid. In addition to these optically active varieties there is an optically inactive form which results when dextro and laevo (levo) varieties are present in equal quantities. It is called racemic mixture or (+-) lactic acid.

Optical isomer lactic acid

The racemic mixture is 50:50 mixture of d and l -isomers and hence have zero optical rotation as the rotation due to one enantiomer cancels the rotation due to the other. That is racemic mixture is optically inactive due to external compensation. The process of conversion of an enantiomer in to a racemic mixture is known as racemisation. Racemisation can be brought about by the action of heat, light and chemical reagent.

Dextro rotatory lactic acid may be obtained from meat extract and is known as sarcolactic acid. With muscular activity glycogen present in muscles break down to sarcolactic acid. During rest sarcolactic acid is converted back to glycogen.

Leavo rotatory lactic acid may be obtained by the fermentation of sucroseby Bacillus Acidi laevolactiti. Ordinary lactic acid in sour milk or manufactured by fermentation or by synthetic method is racemic mixture.

Preparation of Sulphuric Acid (H2SO4)

Production of Sulphuric Acid (H2SO4)

Sulphuric acid is an important chemical used in industry. It is also known as 'King of chemicals'. Sulfuric acid is manufactured by contact process. Contact process Involves the following steps.

Preparation of Sulphurdioxide (SO2)

SO2 is prepared by burning sulphur or sulphide ore in excess of air. It is done in a sulphur burner.

S + O2  ----------->  So2

So2 produced is purified by passing it through

1. Dust precipitator (which removes dust from gas)

2. Water scrubber (which removes soluble impurities)

3. Drying tower (which removes moisture)

4. Arsenic purifier (which removes arsenic impurities)

Oxidation of SO2 to SO3

Purified SO2 gas coming out from arsenic purifier is preheated and admitted to catalytic converter filled with catalyst V2O5. In catalytic chamber the following reversible reaction take place and is known as Contact process.

2SO2 + O2  <========>  2SO3  

According to Le-chatelier's principle, to obtain maximum yield of SO3, low temperature, high pressure and excess of oxygen are required. The optimum condition for the above reaction are
1. a temperature of 720 K
2. a pressure of 2 atm
3. high concentration of reactant
4. Vanadium Pentoxide (V2O5) as catalyst

Conversion of SO3 into Sulfuric acid H2SO4

The SO3 from catalytic converter is absorbed in about 98% H2SO4 resulting in oleum (H2S2O7).

SO3 + H2SO4  ----------->  H2S2O7

SO3 is not directly absorbed in water because it results in mist formation and further absorption become difficult. Oleum is then diluted with water to get Sulphuric acid (H2SO4) of desired concentration.

H2S2O7  +  H2O  ------------>  2H2SO4

Halides of Sulphur

Sulphur hexaflouride (SF6) and Sulfur tetrafluoride (SF4)

Sulphur forms a number of halides in which the oxidation state of sulphur are +1, +2, +4 and +6. The well known halides are

S2X2 (X=F,Cl,Br or I) = oxidation state of S is +1

SX2 (X=F or Cl) = oxidation state of S is +2

Sulphur hexaflouride (SF6)

The oxidation state of Sulphur (s) in Sulphur hexaflouride (SF6) is +6.
Sulphur hexaflouride (SF6) is prepared by direct combination of Sulphur (S) and Flourine (F).

1/8 S8  +  3F2  ----------->  SF6

Sulphur hexaflouride (SF6) has octahedral shape. Sulphur atom is Sp3d2 hybridised.

Sulfur tetrafluoride (SF4)

Sulfur tetrafluoride (SF4) is prepared by fluorination of SCl2 with NaF

3SCl2  +  4 NaF  ------------>  S2Cl2  +  SF4  +  4 NaCl

Sulphur atom is  Sp3d hybridized in SF4 and possess triagonal bipyramidal geometry with one corner is occupied by a lone pair of electrons.

Sulfur dichloride (SCl2)

Sulfur dichloride (SCl2) is formed by saturating S2l2 with chlorine at ordinary temperature.

S2Cl2  +  Cl2  ------------->  2SCl2

In Sulfur dichloride (SCl2), sulphur atom is Sp3 hybridised and has angular structure.

Sulphur monochloride (S2Cl2)

Sulphur monochloride (S2Cl2) is also prepared by direct combination of liquid sulphur and chlorine.

1/4 S8  +  Cl2  ---------->  S2Cl2

The electron diffraction studies have shown a non planer structure for S2Cl2 which is similar to that of H2O2.

Extraction of aluminium

Aluminum is the most abundant metal of earth's crust (8.3%) and exist as oxide and fluoride ores. The metal is extracted from bauxite ore (Al2O3.2H2O). The extraction process involve three stages or steps

step 1 Purification of bauxite
step 2 Electrolytic reduction of Al2O3
step 3 Electrolytic purification of aluminium

1. Purification of bauxite

The bauxite ore contain iron oxide and silicon dioxide as impurities. It is purified by leaching method using concentrated sodium hydroxide solution in which bauxite dissolve forming sodium meta aluminate. On agitating this solution with freshly precipitated Al(OH)3 for several hours Al(OH)3 is precipitated.

NaAlO2  +  2H2O  ------------>  NaOH  +  Al(OH)3

 The precipitate is filtered and dried and NaOH is concentrated and used again for leaching. The aluminium hydroxide precipitate is calcined at 1500oC to obtain pure alumina.

2. Electrolytic reduction of pure alumina

Pure Al2O3 is a bad conductor of electricity and has a very high fusion temperature of 2000oC. Any aluminium formed will vapourise at this temperature as boiling point of aluminum is only 1800oC. Hence alumina mixed with cryolite  Na3AlF6 and CaF2 with a fusion temperature of 900oC is used as the electrolyte. The electrolysis is carried out in an iron tank lined inside with carbon acting as cathode and graphite rods dipped into the electrolyte as anode. Molten aluminium liberated at the cathode gets collected at the bottom of the tank and oxygen liberated at the anode burns away the anode as CO2. The overall reaction may be represented as

2 Al2O3  ------------>  4Al (at cathode) +  3O2 (at anode)

 C(cathode)  + O2  --------------->  CO2

 The anode is replaced from time to time and by adding alumina into the cell and tapping out molten aluminium from the tank the process can be continuously carried out.

Extraction of aluminum

3. Refining of aluminium

 In Hoope's electrolytic method of refining, three liquid layers with differing densities are used. The bottom layer is molten impure aluminium into which Cu and Si has been added to increase density. This molten layer taken is an iron tank lined with carbon is the anode. The electrolyte is a middle layer containing molten mixture of AlF3, BaF2 and NaF. The cathode is the upper layer containing pure molten aluminium. On electrolysis aluminium dissolve from the anode and deposit at the cathode.

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Molecular Orbital Theory: Atomic Structure

Molecular Orbital Theory

To describe the covalent bond formation and nature of electron sharing, two theories have been proposed: Valence Bond Theory (VBT) and Molecular Orbital Theory (MOT). In Valence Bond Theory, only the half filled orbitals of valence shell take part in bond formation and the remaining orbitals retain their identity. But Molecular Orbital Theory (MOT) suggests the combination of all atomic orbitals having comparable energy and proper symmetry. Molecular Orbital Theory (MOT) was developed by F. Hund and R.S Mulliken in 1932. Main postulates of this theory are :

1. Atomic orbitals of comparable energy and proper symmetry combine together to form molecular orbitals.

2. The movement of electrons in a molecular orbital is influenced by all the nuclei of combining atoms. (Molecular orbital is poly centric in nature)

3. The number of molecular orbitals formed is equal to the number of combining atomic orbitals. When two atomic orbitals (AO's) combine together two molecular orbitals (MO's) are formed. One molecular orbital possess higher energy than corresponding atomic orbitals and is called anti bonding molecular orbital (ABMO) and the other has lower energy and is called bonding molecular orbitals (BMO).

4. In molecules electrons are present in molecular orbitals. The electron filling is in accordance with Pauli's exclusion principle, Aufbau principle and Hund's rule.

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Heisenberg's Uncertainty Principle

Definition of Heisenberg's Uncertainty Principle

According to Heisenberg's uncertainty principle, it is not possible to determine precisely both the position and momentum (or velocity) of a moving microscopic particle, simultaneously with accuracy.

Mathematical Expression of Heisenberg's Uncertainty Principle

▵x .▵p => h / 4π

Where  ▵x is uncertainty with regard to the position and ▵p is uncertainty with regard to the momentum of the particle. If ▵x is very small ▵p would be large , that is , uncertainty with regard to momentum will be large. On the other side if we attempt to find out the momentum exactly the uncertainty with regard to position will be large.

Explanation of  Heisenberg's Uncertainty Principle

To determine the position of a small body like electron, it has to be illuminated with electromagnetic radiation. Low energy radiations like ordinary light waves cannot be used to illuminate a small body like electron, since the size of the electron is very small when compared with the wave length of ordinary light. Therefore to irradiate electrons, radiations with shorter wave length are used. When such a high energy radiation is allowed to fall on an electron its velocity changes by a large value. Consequently if we find the position of an electron precisely, there is always an uncertainty in finding the velocity of an electron simultaneously. Thus the determination of position and momentum of a moving electron precisely and simultaneously is impossible.

De-Broglie hypothesis and De-Broglie equation

De-Broglie Hypothesis

In 1924, de-Broglie proposed that matter has a dual character, as wave and as particle.

In Bohr theory, electron is treated as particle. But according to De-Broglie, electron has a dual dual character; both as a material particle and as a wave. He derived an expression for calculating the wave length 'λ' of a particle of mass 'm'  moving with velocity 'v'.

According to this,
wave length = λ =  h / mv  , where 'h' is Planck's constant

This is equation is known as De-Broglie's equation and it is an expression for wave - matter dualism.

The waves associated with particles in motion are called matter waves or De-Broglie waves. They differ from electromagnetic radiations. They have lower velocities, and no electrical and magnetical fields associated with them.

Derivation of  De-Broglie's equation

The de-Broglie's equation can be derived by using the mass energy relationship suggested by Einstein.

 E = mc2
Here 'c' is velocity of light.

Energy of photon  E = hv

∴   hv = mc2

But, v = c /  λ

 ∴  hc / λ  =  mc2

     h / λ  = mc

Hence  λ  =  h / mc

Repalcing 'c' by velocity of a particle 'v'.

     λ  =  h / mv

Since  mv  = p (momentum)

     λ  =  h / p

de-Broglie's wave length of certain particles at 25 o C

Wave length of Electron  60.67 (Ao)
Wave length of Helium atom  0.71 (Ao)
 Wave length of Xenon atom  0.12  (Ao)

properties and uses of Potassium permanganate (KMnO4)

Properties of Potassium permanganate (KMnO4)

1. Potassium permanganate (KMnO4): Action of Heat

Potassium permangante on strong heating gives potassium manganate, manganese dioxide and oxygen.

2 KMnO4 ----------> K2MnO4 + MnO2 + O2

2. Oxidising properties of Potassium permanganate (KMnO4)

Potassium permanganate is a powerful oxidizing agent in alkaline or acidic solution. The relevant half reactions are:

1. Alkaline medium (pH > 7)

MnO4- + 2H2O + 3 e- ----------> MnO2 + 4OH-

2. Acidic medium (pH <7)

MnO4- + 8H+ + 5e- ----------> Mn2+ + 4H2O

A few important oxidizing reactions of Potassium permanganate (KMnO4)

1. In acidic medium potassium permanganate oxidizes green ferrous salts to yellow ferric salts

MnO4- + 8H+ + 5Fe2+ ----------> 5Fe3+ + Mn2+ + 4H2O

2. in acidic medium potassium permanganate oxidizes oxalic acid or oxalate salts to CO2 and water

2 MnO4- + 16H+ + 5 C2O42- -------------> 2 Mn2+ + 10 CO2 + 8 H2O

3. In acidic medium potassium permanganate oxidizes nitrites to nitrate.

2 MnO4- + 6 H+ + 5 NO2- -------------> 2 Mn2+ + 5 NO3- + 3 H2O

4. In acidic medium potassium permanganate oxidises iodides to iodine.

2 MnO4- + 16 H+ + 1 OI- ----------> 2 Mn2+ + 8 H2O + 5 I2

5. In alkaline medium potassium permanganate oxidizes iodides to iodates .

2 MnO4- + H2O + I- ------------> IO3- + 2MnO2 + 2 OH-

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Chemicals in every day life: Dyes

Chemistry in Dyes

Natural dyes are extracted from natural sources. They are used for making coloured fabrics. Probably, the earliest known natural dyes were indigo (a blue dye) and alizarin (a red dye). These were obtained from plants.
Definition of Dyes
A dye is a coloured substance that can be applied in solution or dispersion to a substrate, giving it a coloured appearance.
Usually the substrate is a textile fiber, but it can also be paper, leather, hair, fur, plastic material, wax, a cosmetic base or a foodstuff. Now a days synthetic dyes are used for dyeing purpose.

Classification of Dyes

Dyes are classified either according to their constitution or method of application.

1. Classification of dyes based on Constitution

This classification is based on the distinguishing structural units present in the dye.

1. Azo
2. Nitro
3. Phthalein
4. Triphenyl Methane
5. Indigoid
6. Anthraquinone

2. Classification of dyes based on Application

Depending upon the process of application the dyes are classified as

1. Acid Dyes
2. Basic Dyes

3. Direct dyes
4. Disperse Dyes

5. Fibre reactive dyes
6. Insoluble azo dyes

7. Vat dyes
8. Mordant dyes

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Related post Chemistry in Every day life: Perfumes
Chemicals in Food

Vat dyes, Mordant dyes

Vat Dyes

Vat dyes are insoluble in water and cannot be used directly for dyeing. But on reduction to a leuco form (colour less), they become soluble in an alkali and acquire affinity for cellulose fibres. A solution of the leuco form can be applied for dyeing or printing. On oxidation the original insoluble dye is formed within th structure of the fibre. Indigo and indigosol O are dyes which belong to this class.

Mordant Dyes

Mordant dyes are primarily used for dyeing of wool in the presence of metal ions. The metal ion binds to the fabric and the dye acting as ligand co-ordinates to the metal ion. The same dye in the presence of different metal ions imparts different colours to the fabrics. The colours imparted by Alizarin in presence of different ions are given below

Ions and colours

Al3+ = Rose red

Ba 2+ = Blue

Cr 3- = Brownish red

Mg 2+ = Violet

Sr 2+ = Red

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Fibre Reactive Dyes and Insoluble Azo Dyes

Fibre Reactive Dyes

Fibre Reactive Dyes attach themselves to the fibre by an irreversible chemical reaction. The dyeing is fast and the colour is retained for a long time. The bonding is through the substitution of leaving group of dye via the hydroxy or amino group of fibres like cotton, wool or silk

Insoluble Azo Dyes

Insoluble Azo Dyes are obtained by coupling phenols, naphthols, arlamines, amino naphthols adsorbed on the surface of a fabric with a diazonium salt. Over 60% of the dyes used are Azo dyes. Cellulose, silk, polyester, nylon, polypropylene, polyurethanes, poly acrylonitriles and leather can be dyed by using these dyes. Azo dyes also find use in cosmetics, drugs, biological stains and as indicators in chemical analysis. Use of such dyes for colouring of food stuffs is not permitted.

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Direct Dyes and Disperse Dyes

Direct Dyes

Direct dyes are water soluble dyes. As the name suggests, these dyes are directly applied to the fabric from aqueous solution and are practically suitable for fabrics like cotton, rayon, wool, silk and nylon which from hydrogen bonds with water. Martius yellow and congo red are important example of this class of dyes.

Disperse Dyes

Disperse Dyes
in the form of minute particles of a suspension diffuse into the fabric, get fixed and impart colour. Such dyes are used for dyeing synthetic fibres like polyesters, nylon and polyacrylo nitrile. Many anthraquinone disperse dyes are suitable for application to synthetic polyamide fibres.

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Acid Dyes and Basic Dyes

Acid Dyes

Acid dyes are usually salts of sulphonic acid and can be applied to wool, silk, polyurethane fibres and nylons. The affinity of acid dyes for nylon is higher than that for other types because polycaprolactum fibers fibers contain a higher proportion of free basic amino groups. Acid dyes do not have affinity for cotton. Orange-1 is a versatile acid dye.

Basic Dyes

Basic dyes contain amino group which in acid form water soluble salts. These dyes get attached to the anionic sites present on the fabrics. Such dyes are used to dye reinforced nylons and polyesters. Aniline yellow and malachite green belong to this class of dyes.

To Know more about dyes visit Chemicals in every day life: Dyes

Chemistry in Every day life: Perfumes


Perfumes are the materials which give fragrance. A good perfume should have three essential ingredients. They are
1. Vehicle or Solvent
2. Fixative
3. Odorous substance

1. Vehicle or Solvent

The vehicle or Solvent is used to keep the odour producing substances in solution. Ethanol and water mixture is most commonly used in perfumery.

2. Fixative

Fixative regulate the evaporation of various odoriferous components of perfumes. Sandal wood oil, Benzoin, glyceryl diacetate and esters of cinnamyl alcohols are used as fixative.

3. Odorous Substance

The function of odorous substance is to provide pleasant fragrance to perfume. Odorous substances may be natural or synthetic. Terpenoids like linalool is a natural odoriferous substance. Anisaldehyde (p-methoxy benzaldehyde) is an example for synthetic odoriferous substance.

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Chemicals in Food

Preparation of Potassium permanganate (KMnO4)

Pottassium Permanganate (KMnO4) is prepared from Pyrolusite ore (MnO2). The finely powdered Pyrolusite ore (MnO2) is fused with an alkali metal hydroxide like KOH in the presence of air or an oxidizing agent like KNO3 to give the dark green potassium Manganate (K2MnO4). Potassium manganate disproportionate in a neutral or acidic solution to give potassium permanganate.

2 MnO2 + 4 KOH + O2 ----------> 2K2MnO4 + 2H2O

3 MnO42- + 4H+ ------------> 2MnO4- + MnO2 + 2H2O

Commercially potassium permanganate is prepared by the alkaline oxidative fusion of Pyrolusite ore (MnO2) followed by the electrolytic oxidation of manganate (4) ion.

2 MnO2 + 4KOH + O2 -----------> 2K2MnO4 + 2H2O

MnO42- ------(electrolytic oxidation)----> MnO4- + e-


Potassium permanganate forms dark purple (almost black) crystals, which are iso structural with those of KCLO4. It has weak temperature dependent paramagnetism. the manganate and permanganate ions are tetrahedral. The green manganate is paramagnetic with one unpaired electron but the permanganate is diamagnetic. The pie-bonding takes place by overlaping of P orbitals of oxygen with d orbitals of manganese.

Preparation and properties of Potassium dichromate (K2Cr2O7)

Preparation of Potassium dichromate (

Potassium dichromate (K2Cr2O7) is prepared from chromite ore FeCr2O4. The chromite ore is fused with sodium or potassium carbonate in free access of air.

4FeCr2O4 + 8Na2CO3 + 7O2 -------> 8Na2CrO4 + 2FeO3 + 8CO2

The yellow solution of sodium chromate is filtered and acidified with sulfuric acid to give a solution from which orange sodium dichromate , Na2Cr2O7 2H2O can be crystallized.

2Na2CrO4 + 2H+ ---------> Na2Cr2O7 + 2Na+ + H2O

Sodium dichromate is more soluble than potassium dichromate. Hence sodium dichromate when fused with KCl forms orange crystals of potassium dichromate.

Na2Cr2O7 + 2KCl --------> K2Cr2O7 + 2NaCl

The chromates and dichromates can be inter convertible.

2CrO4 2- + 2H2+ ---------> Cr2O7 2- + H2O

Cr2O7 2- + 2OH- ---------> 2CrO4 2- + H2O

The dichromate ion and chromate ion exist in equilibrium with each other at a pH of 4. Yellow chromate changes into orange dichromate in acid medium and dichromate changes into chromate in basic medium.

2CrO4 2- + 2H+ <-_-_AcidAlkali-_-_> 2HCrO4- (Hydrogen chromate)

2HCrO4-<-_-_AcidAlkali-_-_> Cr2O7 2- + H2O Dichromate (orange)

The chromate ion is tetrahedral and the dichromate ion consists of two tetrahedral sharing at one corner, with Cr-O-Cr bond angle 126 degree.

Properties Potassium dichromate (K2Cr2O7)

Action of heat

Potassium dichromate decomposes on heating to from potassium chromate, chromic oxide and oxygen.

4K2Cr2O7 ------> 4K2CrO4 + 2CrO3 + 3O2

Oxidizing properties

Potassium dichromate is a powerful oxidizing-agent in acidic medium.

Cr2O7 2- + 14H+ + 6 electron -------> 2Cr3+ + 7H2O

A few examples for this oxidizing character in acidic medium are

1. It oxidize iodides to iodine.

Cr2O7 2- + 14H+ + 6I- ------> 2Cr 3+ + 7H2O + 3I2

2. It oxidizes ferrous salts to ferric salts.

Cr2O7 2- + 14H+ + 6 Fe2+ -------> 2Cr 3++ 7H2O + 6Fe3+

3. It oxidizes stannous salts to stannic salts.

Cr2O7 2- + 14H+ + 3Sn 2+ --------> 2Cr 3+ + 7H2O + 3Sn 4+

4. It oxidizes H2S to sulphur

Cr2O7 2- + 8H+ + 3H2S -------> 2Cr 3+ + 7H2O + 3S

Uses of potassium dichromate

Sodium and potassium dichromate are strong oxidizing agents. Potassium dichromate is used as a primary standard in volumetric analysis. It is also used in chrome plating.

Related articles Copper sulphate penta hydrate

For articles about Extraction of metals visit Extraction

Forth flotation process: ore dressing

Concentration Beneficiation by Forth flotation

Forth flotation process

This method is used for the concentration of sulphide ores which are lighter than the impurities. The powdered ore is added to water containing pine oil (frothing agent) and sodium ethyl xanthate (collecting agent). The mixture is strongly agitated by passing compressed air. The sulphide particles stick to the oil droplets forming a forth which rises to the surface. The heavier gangue particles settle to the bottom of the vessel. The forth is skimmed off and heated to separate the oil and the sulphide.

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Leaching: metallurgy

Oxoacids of phosphorus

Phosphorus forms a number of oxoacids. They are hypophosphorous acid (H3PO2), Phosphorous acid (H3PO3), Hypophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7) and meta phosphoric acid (HPO2)n.

1. Hypo phosphorous acid (H3PO2) or phosphinic acid

It is preapred by the oxidation of phosphine by iodine in the presence of calculated amount of water. It is a monobasic acid.

PH3 + 2I2 + 2H2O -----------> H3PO2 + 4 HI

2. Phosphorous acid (H3PO3) or phosphonic acid

It is prepared by hydrolysis of phosphorous trioxide (P4O6). Phosphorous acid is dibasic.
P4O6 + 6H2O ----------> 4H3PO3

phosphorous acid-(phosphonic)-(H3PO3)

3. Hypophosphoric acid (H4P2O6)

It is prepared by controlled oxidation of red phosphorous with sodium chlorite solution, when disodium salt of hypophosphoric acid is formed which then passing through cation exchanger yield hypophosphoric acid. Hypophosphoric acid is tetrabasic.
2P + 2NaClO2 + 2H2O ---------> Na2H2P2O6 + 2HCl
Na2H2P2O6 + 2H -----resin-----> H4P2O6 + 2Na - resin

hypophosphoric acid H4P2O6

4. Orthophosphoric acid (H3PO4)

It is prepared by treating P4O10 with boiled water. It is a tri basic acid.

P4O10 + 6H2O ----------> 4H3PO4

orthophosphoric acid H3PO4

5. Pyrophosphoric acid (H4p2O7)

It is prepared by heating orthophosphonic acid about 250oc. It is a tetrabasic acid.

2H3PO4 ---------> H4P2O7 + H2O

Pyrophosphoric acid H4P2O7

6. Meta phosphoric (HPO3)n.

It is obtained by heating orthophosphoric acid to about 850 K. Metaphosphoric acid does not exist as monomer. It exist as cyclic trimer, cyclic tetramer or polymer.

H3PO4 -------------> HPO3 + H2O

Related articles
Oxides Of Phosphorus

Phosphine gas

Mechanism of Micelle Formation

Definition of Micelles (Associated colloids)

There are some substances which at low concentrations behave as normal strong electrolytes but at higher concentrations exhibit colloidal behavior due to the formation of aggregated particles. These associated particles are called micelles or associated colloids. The formation of micelles take place only above a particular temperature called Kraft temperature (TK) and above a particular concentration called critical micelle concentration (CMC).
Example: Detergents and soaps.

Soap is sodium salt of higher fatty acid like C17H35COONa (sodium stearate). In aqueous solution soap ionizes as The RCOO- ions (C17H35COO-) and Na+ ions.

C17H35COONa ---------> C17H35COO- + Na+

The RCOO- ions however consist of two parts. That is, long hydrocarbon chain R(-C17H35) also called non-polar tail which is hydrophobic and the polar group COO- called polar-ionic head which is hydrophilic. In concentrated solution, these stearate ions get aggregated to form colloidal solution or micelles. For soaps the critical micelle concentration (CMC) is 10-4 to 10-3 mol Lsup>-

Related chemistry article Lyophilic colloids and lyophobic colloids

Lyophilic colloids and lyophobic colloids

Depending upon the nature of interaction between the dispersed phase and the dispersion medium, colloids are classified in to the lyophilic colloids (solvent attracting) and lyophobic colloids (solvent repelling). If water is the dispersion medium, it is called as hydrophilic and hydrophobic colloid respectively.

Lyophilic colloids

The meaning of the word 'lyophilic' is 'liquid-loving' or 'solvent attracting'. That means, these are colloids in which there is strong interaction between the two phases. Lyophilic colloids are those dispersions in which the dispersed phase exhibits a definite affinity for the medium and as a results extensive solvation of the colloidal particles takes place. They are directly formed by mixing the two phases.Eg :- Gum, soap, starch, gelatin, rubber etc.
These sols are also called reversible sols. Because, if the dispersion medium is separated from the dispersed phase, the sol can be reconstituted by simply mixing with the dispersion medium.

Lyophobic colloids

The word 'lyophobic' means 'liquid hating', ie, in these sols there is little or no interaction between the two phases. Lyophobic sols are those dispersions in which there is very little attraction between dispersed phase and dispersion medium, They cannot be prepared by simply mixing the two phases. Eg :- Dispersion of metals in water, colloidal hydroxides etc.
They are irreversible in nature. Because, once precipitated, they do not given back the colloidal sol by simple addition of the dispersion medium.

Comparison between lyophilic and lyophobic

Lyophilic colloidal particles are easily solvated. Lyophobic colloidal particles are weakly solvated. Small quantities of electrolytes have little effect but large amount may cause salting out in lyophilic sol. In Lyophobic sol small quantities of electrolytes causes precipitation. The particles cannot be readily detected in the ultra microscope in lyophilic sol. The particles are easily detected in the ultra microscope in Lyophobic sol. Particles may migrate in either direction or not at all in an electric field in lyophilic sol. In lyophobic sol particles migrate in only one direction in an electric field. In lyophilic sol surface tension is generally lower than that of dispersion medium. In lyophobic sol surface tension is almost similar to that of the dispersion medium. Lyophilic sols are reversible. Lyophobic sols are irreversible.

Electrochemical Theory of Rusting

Corrosion Of Iron

Corrosion is the process in which a metal is destructed as a result of its reaction with environment. Corrosion of iron is known as rusting. Rusting is the hydrated ferric oxide. Other examples for corrosion are tarnishing of silver and development of green coating on copper and bronze. In corrosion metals undergo anodic oxidation to metal oxides.

Electrochemical theory of rusting

The rusting of iron is an electrochemical process involving the following steps.

The moister containing CO2 acts as electrolyte.

H2O + CO2 ------> H2CO3
H2CO3 ------> 2H+ + CO32-

The iron is oxidized by the removal of electrons and acts as the anode.

Fe ------> Fe2+ + 2electron

The H+ ions from the electrolyte accept electrons from the adjacent areas on metal surface and function as cathode.

4H+ + 4electron ------> 2H2

The atmospheric oxygen moves hydrogen as water.

2H2 + O2 ------> 2H2O

Adding the above two equations,

4H+ +O2 + 4electron ------> 2H2O

Fe2+ formed at the anode is further oxidized to Fe3+ by atmospheric oxygen in presence of moisture.

4Fe2+ + O2 + 4H2O ------> 2Fe2O3 + 8H+

The ferric oxide gets hydrated to form rust.

Fe22O3 + xH2O ------> Fe2O3.xH2O (rust)

Rust is chemically hydrated iron oxide (Fe2O3.xH2O). It does not stick to the surface of iron. Hence fresh surface of iron is always exposed and undergo further rusting. Corrosion causes several damages to buildings, bridges, ships and other objects made of metals. Some of the important methods used to prevent corrosion of metals are barrier protection, Sacrificial protection, Electrical protection, using anti rust solution.

Prevention of Corrosion Methods

1. Barrier protection

In this method a barrier is placed between metal and atmosphere. This is actually done by coating the metals surface with paint oil or grease. The barrier avoids the direct contact of the metal surface with the environment and hence prevents corrosion.

2. Sacrificial Protection

In this method the iron object is covered with a thin coating of metal like zinc which is more reactive than iron. Here the active metal which is coated will act as anode and undergo oxidation in preference to iron. The process of coating iron objects with zinc is called galvanization.

3. Electrical Protection or Cathodic Protection

In this method, the iron object which is to be protected from corrosion is made cathode by coupling it with another more active metal. Here the active metal acts as anode and protect the iron article from destruction. The iron object will remain protected as long as the active metal in present.

4. Using anti rust Solution

Alkaline phosphate and alkaline chromates are used as anti rust solutions. When anti rust solution are applied on iron objects, the iron phosphate or iron chromate formed are act as insoluble and heat resistant coating and prevent rusting.

Prepration of phenol

Preparation of phenol from benzene derivatives

Phenol was first isolated in the early nineteenth century from coal tar. Nowadays, phenol is commercially produced synthetically. In the laboratory, phenols may be prepared from benzene derivatives by any of the following methods.

1. From sodium benzene sulphonate

Benezene sulphonic acid when treated with NaOH gives its sodium salt. Sodium benzene sulphonate. This when fused with NaOH at temperature between 570-620 K, gives sodium phenoxide, which on hydrolysis with dilute mineral acid gives phenol.


2. From Benzene diazonium chloride

Benzene diazonium chloride is formed by treating aniline with nitrous acid (NANO2 + HCl) at 273-283 K temperature. On warming an aqueous solution of benzene diazonium chloride, it is hydrolysed to form phenol.


3. From Chlorobenzene (Dow’s process)

Chlorobenzene on heating with 10% aqueous solution of NaOH at about 623K under 200 atmospheric pressure in the presence of copper salt catalyst, sodium phenoxide is formed. This on acidification with dilute HCl undergoes hydrolysis to give phenol. The method is called Dow’s process.


For industrial preparation of Phenol Visit

Related post Chemical properties of Alcohols and Phenols

Industrial Preparation of Phenol

Preparation of Phenol From Coal Tar

Phenol is commercially prepared from the middle oil fraction (443-503K) of coal tar distillate in which it occurs with cresols and naphthalene. First naphthalene is removed by chilling the fraction. The remaining oil is now treated with H2SO4 to remove basic impurities and phenol is then extracted with dilute caustic soda. The aqueous layer is separated and phenol is precipitated with H2SO4 or CO2. It is finally purified by distillation.

Preparation of Phenol From

Nowadays, phenol is manufactured from the hydrocarbon cumene. Cumene (isopropyl benzene) is first prepared from benzene and propene by Friedel-Crafts reaction in presence of phosphoric acid of aluminum oxide. Cumene is oxidized in presence of air to cumene hydroperoxide, which is then converted to phenol and acetone by treating it with dilute acid. Acetone, a byproduct of this reaction, is also obtained in large quantity by this method.

Phenol has a melting point of 314 K and it is moderately soluble in water (8% at 298K).

Uses of Phenol

Phenol is a strong antiseptic. It is widely used as a raw material for the manufacture of important dyes, drugs and pharmaceuticals, polymers like Bakelite a and a number of organic chemicals like salicylic acid, picric acid, phenolphthalein etc.

For preparation of Phenol by chemical method visit Prepration of phenol

Reaction of Ether with Hydrogen Iodide (HI)

Chemical properties of Ethers
(With HI)

On heating with concentrated Hydrogen iodide (HI) the C-O bond in ethers breaks forming alcohol and alkyl iodide. For example,

C2H5 -O-C2H5 + HI ------------> C2H5 - I + C2H5OH

On boiling with excess of concentrated Hydrogen iodide (HI), Alkyl iodide is formed.

C2H5 -O-C2H5 + 2HI ------------> 2C2H5I + H2O

In the case of mixed ethers with two different alkyl groups, the site of cleavage and hence the alcohol and alkyl iodide that form depend on the nature of the alkyl groups.

When one group is methyl and the other is primary or secondary alkyl group, it is the lower alkyl group that forms alkyl iodide due to steric factors.
For Example,

Ehtyl methyl ether reaction with Hydrogen iodide Froming Ehtyl alcohol and Methyl ioidie

reaction of ether with Hydrogen iodide (HI)

When one group is methyl and the other alkyl group is a tertiary group, the halide formed is a tertiary group, the halide formed is a tertiary halide.
For Example,

reaction of ether with Hydrigen iodide(HI)

It is because the attack by I- takes place at that carbon of alkyl group, which has a greater electron pushing inductive effect and a lower electron density.

Phenolic ethers react with HI to form phenol and alkyl iodide. This can be attributed to the resonance and steric effects of the benzene ring.

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Manufacture of Ethanol from Molasses

Preparation of Ethanol (Drinking Alcohol)

Ethanol is the most important member of the alcohol series. Ethanol is prepared industrially by the fermentation of sugars in molasses, sugarcane or fruits such as grapes or starch obtained from various grains. Fermentation is the oldest method of making ethanol from sugars. It is the slow decomposition of complex organic compounds into simple compounds by the action of biological catalysts called enzymes.

Manufacture of Ethanol from Molasses

Molasses is the mother liquor left behind after the crystallization of sugar from sugarcane juice. It contains about 40% non-crystallizable sugar.
Mollasses is first diluted to about 10% concentration of sugar. Then, calculated amount of yeast is added and kept at an optimum temperature of about 305K. Yeast provides the enzymes invertase and Zymase which can cause fermentation. The enzyme invertase catalyses the hydrolysis of sugar into glucose and fructose. Glucose and fructose are decomposed into ethanol in the presence of the enzyme zymase. Ultimately, a dilute solution of ethanol (8-10%), called 'wash' is obtained.

Chemical Equations

C12H22O11 + H2O ------invertase------> C6H12O6 (glucose) + C6H12O6 (fructose)

C6H12O6 (glucose / fructose) -----zymase-----> 2C2H5 - OH (ethanol) + 2CO2

Preparation of Methanol

Industrial Preparation of Methanol

Methanol, CH3OH, which is also known as 'Wood alcohol' or 'Wood spirit'. Methanol is produced by the destructive distillation of wood. Today, most of the methanol is produced by catalytic hydrogenation of carbon monoxide at high pressure and temperature and in presence of Cu-ZnO-Cr2O3 catalyst.

Co + 2H2 ----(Cu-ZnO-Cr2O3, 200-300 atm, 573-673 K)------> CH3OH

Methanol is a colourless liquid with boiling point 337 K. It is highly poisonous in nature. Injection of even small quantities of methanol can cause blindness and in large quantities, even death.

Uses of Methanol

Methanol is used as a solvent on paints, varnishes etc. and methanol is chiefly for the preparation of formaldehyde. Methanol is also used for denaturing ethanol.

For more visit Preparation of alcohol

Ether forming Peroxides (Auto oxidation)

Reaction of ethers with atmospheric Oxygen

Ethers form peroxides by the action of atmospheric oxygen or ozonised oxygen due to co-ordination of one lone pair of the ethereal oxygen with another oxygen atom

For example,

C2H5O2H5 + O ------------> (C2H5)2O (diethyl ether Peroxide)---> O

These peroxides are unstable compounds and decomposes violently on heating. Hence, ethers should never be evaporated to dryness. it is essential to remove the peroxides by washing before distilling the ether. This can be done by washing the ether with a solution of ferrous sulphate.

For Chemical properties of ethers visit

Reaction of Ether with Sulphuric Acid

Chemical Properties of Ethers (with H2SO4)

On heating with dilute sulfuric acid under pressure, ethers are hydrolysed to alcohols.
For example,

C2H5OC2H5 + H2O ----(dil.H2so4,high pressure)-----> 2C2H5OH

Mixed ethers under similar conditions give a mixture of alcohols.

CH3OC2H5 + H2O ------(dil.H2so4,high pressure)------>C2H5OH + CH3OH

But if concentrated sulfuric acid is used, then the products are alcohol and alkyl hydrogen sulphate.

C2H5OC2H5 (Diethyl ether) -----(heat, conc. H2SO4)-----> C2H5OH (ethanol)+ C2H5OSO2OH (ethyl hydrogen sulphate)

Ethers containing secondary and tertiary alkyl groups form alkenes with conc. sulphuric acid.
For example

reaction of H2SO4 with Ether

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Chemical Properties of Ether

The functional group in ethers (-O-) is comparatively inert with respect to the -OH functional group in alcohols and phenols even though the oxygen atom in each of the groups has two lone pairs of electrones. Therefore, ethers are not easily attacked by alkalies, dilute mineral acids, PCl5, metallic sodium etc. under ordinary conditions. But they undergo chemical reactions under specific conditions.

1. Cleavage of C-O bond in ethers

The cleavage of C-O bond in ethers takes palce under drastic conditions with excess of hydrogen halides. The reaction of dialkyl ether gives two alkyl halide molecules.

R-O-R + 2HX -------------> 2RX + H2O

Alkyl aryl ethers are cleaved at the alkyl-oxygen bond. The reaction yields phenol and alkyl halide.

Ethers with two different alkyl groups are also cleaved in the same manner.

R-O-R' + H-X ------------> R-X + R'-OH

The order of reactivity of hydrogen halides is as follows: HI > HBr > HCl.

1. Reaction with HI

2. Reaction with H2SO4

3. Formation of Peroxides