| What are racemic mixtures? How are they obtained? Discuss one method of their |
| resolution. |
In chemistry, a racemic mixture is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule. The first known racemic mixture was racemic acid, which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. A sample with only a single enantiomer is an enantiomerically pure, enantiopure or homochiral compound.
A racemic mixture is denoted by the prefix (±)- or dl- (for sugars the prefix dl- may be used), indicating an equal (1:1) mixture of dextro and levo isomers. Also the prefix rac- (or racem-) or the symbols RS
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Suggest the reaction that can best be used to prepare following ethers by Williamson ether synthesis
(a) CH3CH 2— O— CH= CH2
(b) 
Write the mechanism for the Haloform reaction.
What is resonance energy? Explain taking the example of benzene.
How will you prepare the following ?
(i) 10 -Hexyne from ethyne
(i) Ethanol from ethyne
(ii) 3-Hexanone from 3-hexyne.
Explain the following:
(i) Alkanes with odd number of carbon atoms have low melting point than those with an even number.
(ii) Wurtz reaction is not very useful when two different alkyl halides are used.
Explain Hell-Vollhard-Zelinski reaction. Also illustrate its synthetic importance.
Predict the product(s) of the following reactions:
(i) Nitration of azole
(ii) Friedel-Crafts acylation of pyridine
(iii) Reduction of pyrrole with zinc and ethanoic acid.