Question 1

Which of the following best describes the key bond-forming step in the synthesis of nylon 66, as shown in the first image?

Accepted Answer

A nucleophilic acyl substitution between a diamine and a diacid chloride

Question 2

In the preparation of polyesters as shown in the second image, which functional groups react to form the polymer backbone?

Accepted Answer

A diol and a diacid

Question 3

Which of the following statements about the hydrolysis of amides is correct?

Accepted Answer

Hydrolysis of amides requires more severe conditions than esters due to the poor leaving group ability of the amide nitrogen.

Question 4

Which IR absorption would you expect to be strongest and most diagnostic for a carboxylic acid derivative?

Accepted Answer

C=O stretch at $$1650-1850\ \mathrm{cm}^{-1}$$

Question 5

A compound shows two strong IR absorptions at approximately $$3350\ \mathrm{cm}^{-1}$$ and $$3180\ \mathrm{cm}^{-1}$$, and a strong absorption at $$1690\ \mathrm{cm}^{-1}. $$What is the most likely functional group present?

Accepted Answer

1° amide

Question 6

Which of the following best explains why the reduction of an amide with $$\mathrm{LiAlH}_4$$ yields an amine rather than an alcohol?

Accepted Answer

The amide nitrogen remains attached to the carbon skeleton during reduction.

Question 7

Which of the following polymers is most likely to be biodegradable due to its susceptibility to hydrolysis?

Accepted Answer

Poly(lactic acid)

Question 8

Refer to the third image. Which monomer would produce a polymer with the repeating unit $$\mathrm{\left[-OCH_2CO-\right]_n}$$?

Accepted Answer

Glycolic acid

Question 9

A student analyzes an IR spectrum and observes a strong absorption at $$1735\ \mathrm{cm}^{-1}$$ and a broad absorption at $$3200-3500\ \mathrm{cm}^{-1}. $$Which functional group is most likely present?

Accepted Answer

Carboxylic acid

Question 10

Which of the following $$^1H $$NMR chemical shift ranges is most characteristic for protons adjacent to the nitrogen in an amide?

Accepted Answer

$$\delta\ 2.2-3.0$$

Question 11

A $$^1H $$NMR spectrum of a compound shows a broad signal between $$\delta\ 6.0-9.0$$ and another signal at $$\delta\ 2.3. $$Which compound is most likely being analyzed?

Accepted Answer

An amide

Question 12

Which of the following is a correct statement about the $$^{13}C $$NMR chemical shift of the carbonyl carbon in carboxylic acid derivatives?

Accepted Answer

It appears in the range $$\delta\ 160-180$$

Question 13

Which of the following best explains why an excess of amine is used in the preparation of amides from acid chlorides?

Accepted Answer

To neutralize the HCl byproduct and drive the reaction to completion

Question 14

Which IR spectrum (images 5, 6, or 7) would you expect for N,N-dimethylpropanamide, a 3° amide?

Accepted Answer

Image 7, which lacks N-H stretches in the $$3300-3500\ \mathrm{cm}^{-1}$$ region

Question 15

Which of the following best describes the difference in $$^1H $$NMR spectra between ethyl acetate and N-ethylacetamide?

Accepted Answer

N-ethylacetamide shows a broad downfield signal due to the N-H proton, which is absent in ethyl acetate.

Question 16

Which of the following is a correct statement about the IR spectrum of a 2° amide?

Accepted Answer

It shows a single N-H stretch near $$3300\ \mathrm{cm}^{-1}.$$

Question 17

Which of the following best explains why polyesters such as poly(lactic acid) are considered biodegradable?

Accepted Answer

Their ester linkages are susceptible to hydrolysis by soil microorganisms.

Question 18

Which of the following is the correct order of carbonyl stretching frequencies (from highest to lowest) for the following carboxylic acid derivatives: acid chloride, ester, amide?

Accepted Answer

Acid chloride \u003e ester \u003e amide

Question 19

A polymer is synthesized from a diamine and a diacid chloride. Which type of polymer is formed?

Accepted Answer

Polyamide

Amides, Step-Growth Polymers, and Spectroscopy of Carboxylic Acid Derivatives

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