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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 (-) Adrenali...

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 mixt...

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 cont...

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. Mes...

Optical Isomers of lactic acid In lactic acid CH 3 - 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 . 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 ...

Production of Sulphuric Acid (H 2 SO 4 ) 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 (SO 2 ) SO 2 is prepared by burning sulphur or sulphide ore in excess of air. It is done in a sulphur burner. S + O 2   ----------->  So 2 So 2 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 SO 2 to SO 3 Purified SO 2 gas coming out from arsenic purifier is preheated and admitted to catalytic converter filled with catalyst V 2 O 5 . In catalytic chamber the following reversible reaction take place and is known as Contact process . 2SO 2 + O 2   <========>...

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 S 2 X 2 (X=F,Cl,Br or I) = oxidation state of S is +1 SX 2 (X=F or Cl) = oxidation state of S is +2 Sulphur hexaflouride (SF6) The oxidation state of Sulphur (s) in Sulphur hexaflouride ( SF 6 ) is +6. Sulphur hexaflouride (SF6) is prepared by direct combination of Sulphur (S) and Flourine (F). 1/8 S 8   +  3F 2   ----------->  SF 6 Sulphur hexaflouride ( SF 6 ) has octahedral shape. Sulphur atom is Sp 3 d 2 hybridised. Sulfur tetrafluoride (SF4) Sulfur tetrafluoride (SF4) is prepared by fluorination of SCl 2 with NaF 3SCl 2   +  4 NaF  ------------>  S 2 Cl 2   +  SF 4   +  4 NaCl Sulphur atom is  Sp 3 d hybridized in SF 4 and possess triagonal bipyramidal geometry with one corner is occupied by ...

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 (Al 2 O 3 .2H 2 O). The extraction process involve three stages or steps step 1 Purification of bauxite step 2 Electrolytic reduction of Al 2 O 3 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. NaAlO 2   +  2H 2 O  ------------>  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 1500 o C to obtain pure alumina. 2. Electrolytic reduction of pure alumina ...