Acids and Derivatives Physical Properties 1. Experiments show that the molecular

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Acids and Derivatives Physical Properties 1. Experiments show that the molecular weight of acetic acid in the vapor state is approx. 120. Explain the discrepancy between this experimental value and the true value of approx. 60. 2. The pK1 for all of the dicarboxylic acids is smaller than the pKa for monocarboxylic acids with the same number of carbon atoms. Explain. 3. Where does the carbonyl stretch of an ester appear in the IR? How about that of an amide? Explain the difference. 4. The pKa of p-(trifluoromethyl)benzoic acid is 3.6. Would you expect the trifluoromethyl substituent to be an activating or deactivating group in the Friedel-Crafts reaction? 5. Would you expect an amide N-H to be more or less acidic than an amine N-H? Explain 6. Rank the following in terms of increasing boiling point and explain your ranking. CH

Explanation / Answer

Ans 1 :

The chemical formula of acetic acid is CH3COOH.

So when the molar masses of its constituent atoms are added we get the molecular weight of the acid molecule as 60.

In the vapor state, the molecules of the acid dimerise, due to hydrogen bonding. So the molecular weight calculated in the experiment will be abnormally higher.

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