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Replacement reaction of benzene diazonium chloride by halide ion When the solution of freshly prepared benzene diazonium salt is trated with a mixture of cuprous chloride or cuprous bromide in presence of concentrated HCL or HBr, we get chlorobenzene or bromobenzene. This reaction is known as Sandmaeyer's reaction . Alternatively the same reaction can be done by copper powder and cone. HX instead of cuprous halide and this modified reaction is called Gatterman reaction . Indobenzene can be prepared from benzene diazonium salt by reacting with KI solution. Replacement with fluoride is known as Balz Schiemann reaction .In this benzene diazonium salt is reacted with fluoroboric acid heated to get fluorobenzene . Preparation of aryl halides from diazonium salt by replacement gives pure aryl halides and provides important synthetic route for preparation of aryl iodides and aryl fluorides. Visit http://www.entrancechemistry.blogspot.in/2013/05/reactions-of-ben...

Diazonium salt reactions Diazonium salts have N2 X functional group attached to an aryl group. They are highly unstable and are mainly used as a synthetic intermediate for various compounds. Alkyl diazonium salt do not exist even below 00C.   Nomenclature of Diazonium salt   The name is obtained by adding diazonium chloride, sulphate etc. to the name of parent hydrocarbon. Methods of Preparation Aromatic diazonium salts are prepared from aromatic primary amines. aromatic primary amine is taken in the ice-cold solution of HCL and adding sodium nitrite at 00C we get aromatic diazonium salt. This reaction is known as diazotisation. Diazonium salt are highly unstable and they are not stored and they are not stored and are used immediately after their preparation.

Cyanides are the compounds with functional group -CN and can be regarded as the derivatives of hydrogen cyanide (HCN). The cyanide group is an ambident group. This means cyanide group can attach to alkyl or aryl group through both carbon atoms as well as nitrogen atom. Thus the compounds obtained by replacement of the H-atom of hydrogen cyanides by alkyl or aryl group are called organic cyanides or nitriles. Isocyanides are the compounds isomeric with cyanides and can be regarded as derived from Hydrogen isocyanide by replacement of H by alkyl or aryl group.

Reaction of nitrous acid with Aromatic Primary amines At 273 - 278 K, atomic primary amines react with sodium nitrite and dilute HCl, to give aromatic diazonium salts. For example, aniline forms benzene diazonium chloride. Aromatic diazonium salts are stable only at low temperature. Hence at higher temperature, aromatic primary amine gives phenols. Reaction of nitrous acid with Aromatic Primary amine Aliphatic diazonium salts are highly unstable and hence alcohols are obtained when aliphatic primary amines are reacted with nitrous acid.

Chemical properties of amines In most of its reaction, amines act as a nucleophile or a base due to lone pair on nitrogen. In aromatic amines, due to resonance, the -NH 2 group make the ring more susceptible to electrophilic substitution at ortho and para position. Important reactions of amines are classified as :   1. Salt formation Amines are soluble in mineral acids and carboxylic acids, due to the formation of soluble ammonium salts. RNH 2 + HCl  ------->  RNH 3 + Cl - C 6 H 5 NH 2 --------> C 6 H 5 NH 3 + Cl - 2. Alkylation Alkyl halides when react with primary or secondary amines undergo nucleophilic substitution. When HX is removed, secondary or tertiary amine formed will again reacts with alkyl halide froming tertiary amine and finally quaternary ammonium salt.   3. Acylation 4. Reaction with carbonyl compounds 5. Carbylamine reaction 6. Reaction with nitrous acids With nitrous  acid primary, secondary and ter...

Reaction of Amine with Carbonyl compunds Only primary amines react with aldehydes and ketones and condensation products are obtained. These condensation products are known as imines or Schiffs bases. R-CHO (aldehyde) + RNH 2   ---------> RCH = N-R (aldimine) R 2 CO (ketone) + R-NH 2 --------> R 2 C = N-R (ketimines) Imines can be reduced to secondary amines. This reaction, in turn, can be used to convert a primary amine to secondary amine. RCH = NR  ------ (H 2 / Ni) -----> R-CH 2 -NH-R  (Secondary amine) R 2 C = N-R ------ (H 2 / Ni) -----> R 2 CH-NH-R For more visit P roperties of Amines

Acylation of amines mechanism Both aliphatic and aromatic primary and secondary amines undergo N-acetylation. This acetylation can be effected using acid halides or anhydrides in presence of a base (pyridine) and the product obtained is an amide. Base remove HCl and prevent protonation of amine. Acylation of primary amine Acylation of Secondary amine Since amides formed are not basic, they do not under go further actylation. Acid chlorides are stronger acetylating agent than acetic anhydride. In tertiary amines there is no replaceable hydrogen and they do not undergo acylation. 

Physical Properties of Amine 1. Physical state of Amine Lower amines are gases while higher members are mostly liquids. Amines are almost unpleasant, having fishy smell. In the pure state amines are colourless, but in certain case they become coloured due to oxidation and mixing of impurities. 2. Boiling point In amines, there are polar N-H bonds. Hence, in general they are polar. More over, in amines, inter molecular hydrogen bonds are present, leading to high boiling points in comparison to corresponding hydrocarbons of the same molar mass. Primary and secondary amines can form hydrogen bonding hence they higher boiling points than isomeric tertiary amines. 3. Solubility in water All the three classes of amines can form hydrogen bond with water. Hence they are soluble in water. But higher amines are least soluble due to the non-polar effect of big alkyl groups. Due to weaker hydrogen bonds solubility of amines in water is less than that of alcohols.

Distinction between primary, secondary and tertiary amine Using Carbylamine Reaction Primary amine (both aliphatic and aromatic) when warmed with chloroform and alcoholic KOH, gives isocyanides ( carbylamines ). This is called c arbylamine reaction . Carbylamines has an offensive smell. This reaction is answered only by primary amine and hence to distinguish primary amine from other classes of amines . In general R-NH 2   +  CHCl 3   +  3KOH  --------->  RNC (carbylamine) +  3KCl + 3H 2 O

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 (C 6 H 5 SO 2 Cl). 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. RNH 2 (primary amine)  +  C 6 H 5 SO 2 Cl ( Hinsberg reagent ) ------------>  R-NH-SO 2 -C 6 H 5   ------(NaOH)---> R-N - Na + -SO 2 C 6 H 5 (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. R 2 NH (secondary amine)  +  C 6 H 5 SO 2 Cl ( Hinsberg reagent ) ------------> R 2 NSO 2 C 6 H 5 (precipitate)  -----(NaOH)---> insoluble (no reaction) 2. Reac...

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 ...

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 H 2 SO 4 to remove basic impurities and phenol is then extracted with dilute caustic soda . The aqueous layer is separated and phenol is precipitated with H 2 SO 4 or CO 2 . It is finally purified by distillation. Preparation of Phenol From Cumene 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 3...

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, C 2 H 5 -O-C 2 H 5 + HI ------------> C 2 H 5 - I + C 2 H 5 OH On boiling with excess of concentrated Hydrogen iodide (HI), Alkyl iodide is formed. C 2 H 5 -O-C 2 H 5 + 2HI ------------> 2C 2 H 5 I + H 2 O 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, 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, It is because the attack by I- takes place at that carbon of alkyl group, which has a greater electron pus...

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 ethano...

Industrial Preparation of Methanol Methanol , CH 3 OH, 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-Cr 2 O 3 catalyst. Co + 2H 2 ----(Cu-ZnO-Cr 2 O 3 , 200-300 atm, 573-673 K)------> CH 3 OH 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

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, C 2 H 5 O 2 H 5 + O ------------> (C 2 H 5 ) 2 O (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 http://entrancechemistry.blogspot.com/2012/07/chemical-properties-of-ether.html

Chemical Properties of Ethers (with H 2 SO 4 ) On heating with dilute sulfuric acid under pressure, ethers are hydrolysed to alcohols. For example, C 2 H 5 OC 2 H 5 + H 2 O ----( dil.H2so4,high pressure )-----> 2C 2 H 5 OH Mixed ethers under similar conditions give a mixture of alcohols. CH 3 OC 2 H 5 + H 2 O ------( dil.H2so4,high pressure )------>C 2 H 5 OH + CH 3 OH But if concentrated sulfuric acid is used, then the products are alcohol and alkyl hydrogen sulphate. C 2 H 5 OC 2 H 5 (Diethyl ether) -----( heat, conc. H2SO4 )-----> C 2 H 5 OH (ethanol)+ C 2 H 5 OSO 2 OH (ethyl hydrogen sulphate) Ethers containing secondary and tertiary alkyl groups form alkenes with conc. sulphuric acid. For example For more about chemical reaction of ether visit http://entrancechemistry.blogspot.in/2012/07/chemical-properties-of-ether.html

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, PCl 5 , 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 + H 2 O 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 ...

Lower members of ethers are gases while higher members are volatile with pleasant smell. The C-O bond in ethers are polar. They are nonlinear (angular) molecules with C-O-C bond angle of about 110 0 . Therefore, ethers are polar compounds and have a net dipole moment. For example, dipole moment of dimethyl ether is 1.3D. Ethers are isomeric with alcohols. But they do not show hydrogen bonding and association because of their low polarity. The weak polarity of ethers do not appreciably affect their boiling points which are comparable to those of alkanes of comparable molecular mass but are much lower than the boiling points of isomeric alcohols. Ethers containing upto 3 carbon atoms are soluble in water due to their hydrogen bond formation with water molecules. The increase in the size of the alkyl group decreases the polar nature of C-O bond and hence it decreases the hydrogen bonding with water. As a result solubility of ethers decreases with increase in the number of carbon atoms. Et...

Preparation of ethers using sodium alkoxide This is an important laboratory method for the preparation of symmetrical and unsymmetrical ethers. In this method, ethers are prepared by heating an alkyl halide with sodium alkoxide. Ethers containing substituted alkyl groups (secondary or tertiary) may also be prepared by this method. The reaction involves a nucleophilic substitution of halide ion by an alkoxide ion. Thus, good results are obtained if the alkyl halide is primary. If a tertiary alkyl halide is used, an alkene is the only reaction product and no ether is formed. For example, the reaction of CH3CONa with (CH3)3 C-Br gives exclusively 2 -methyl propene. It is because alkoxides are not only nucleophiles but also strong bases. They react with alkyl halides leading to elimination reactions. Since halogen attached to the benzene ring is not reactive, in order to prepare an alkyl aryl ether, a mixture of alkyl halide and sodium phenoxide must be heated. For example, ethyl phenyl et...