Q: Which IR spectrum would you expect for benzonitrile based on the characteristic absorption of the nitrile group?

A strong, sharp absorption near $$2230-2250\ \text{cm}^{-1}$$

Q: Which of the following statements about the $$\mathrm{C\equiv N}$$ stretch in IR spectroscopy is correct?

It appears as a strong, sharp absorption at $$2230-2250\ \text{cm}^{-1}.$$

Question 1

Which IR spectrum would you expect for benzonitrile based on the characteristic absorption of the nitrile group?

Accepted Answer

A strong, sharp absorption near $$2230-2250\ 	ext{cm}^{-1}$$

Question 2

What is the major product when acetonitrile is treated with $$\mathrm{LiAlH}_4$$ followed by water?

Accepted Answer

Ethylamine ($$\mathrm{CH_3CH_2NH_2})$$

Question 3

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

Accepted Answer

Acidic hydrolysis of nitriles is milder and typically preferred over basic hydrolysis.

Question 4

A student treats 1-bromopropane with sodium cyanide in DMSO. What is the major organic product?

Accepted Answer

Butanenitrile ($$\mathrm{CH_3CH_2CH_2CN})$$

Question 5

Which of the following best describes the $$^1H $$NMR chemical shift range for protons adjacent to a nitrile group?

Accepted Answer

$$\delta\ 2.0-2.7$$

Question 6

Which reaction sequence would convert a primary amide to a nitrile?

Accepted Answer

Dehydration with $$\mathrm{$$SOCl_2$$}$$

Question 7

A compound shows a strong IR absorption at $$1710\ 	ext{cm}^{-1}$$ and a broad absorption from $$2500-3300\ 	ext{cm}^{-1}. $$Which functional group is most likely present?

Accepted Answer

Carboxylic acid

Question 8

Which of the following is a correct statement about the McLafferty rearrangement in mass spectrometry?

Accepted Answer

It occurs in carboxylic acids with gamma hydrogens, producing a neutral alkene and a charged fragment.

Question 9

Which $$^{13}C $$NMR chemical shift is most diagnostic for the nitrile carbon?

Accepted Answer

$$\delta\ 115-130$$

Question 10

A student observes a strong IR absorption at $$2250\ 	ext{cm}^{-1}$$ and no significant absorption near $$3300\ 	ext{cm}^{-1}. $$Which compound is most likely present?

Accepted Answer

A nitrile

Question 11

Which of the following best describes the product of the reaction of a nitrile with a Grignard reagent followed by hydrolysis?

Accepted Answer

A ketone

Question 12

Which of the following is the correct IUPAC name for the compound $$\mathrm{CH_3CH_2CH_2CN}$$?

Accepted Answer

Butanenitrile

Question 13

Which of the following statements about the $$\mathrm{C\equiv N}$$ stretch in IR spectroscopy is correct?

Accepted Answer

It appears as a strong, sharp absorption at $$2230-2250\ 	ext{cm}^{-1}.$$

Question 14

A mass spectrum of butanoic acid shows a prominent peak at $$m/z = 60. $$What is the most likely origin of this peak?

Accepted Answer

McLafferty rearrangement fragment

Question 15

Which of the following is a limitation of preparing nitriles via $$\mathrm{S_N2}$$ displacement with cyanide ion?

Accepted Answer

The reaction is limited to primary and some secondary alkyl halides due to steric hindrance.

Question 16

Which of the following compounds would show a $$^1H $$NMR signal at $$\delta\ 10.5-12.0$$ that disappears upon addition of $$\mathrm{D_2O}$$?

Accepted Answer

Benzoic acid

Question 17

Which of the following best describes the fragmentation pattern of carboxylic acids in mass spectrometry?

Accepted Answer

Alpha cleavage to form an acylium ion and McLafferty rearrangement if gamma hydrogens are present.

Question 18

Which of the following is the correct product when benzonitrile is hydrolyzed under acidic conditions?

Accepted Answer

Benzoic acid

Question 19

A compound with the formula $$\mathrm{C_7H_5NO}$$ shows a strong IR absorption at $$2230\ 	ext{cm}^{-1}. $$What is the most likely structure?

Accepted Answer

Benzonitrile

Nitriles and Carboxylic Acids: Structure, Synthesis, and Spectroscopy

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