Chapter 18

Which of the following correctly describes the bond angle and hybridizations present in formaldehyde?

• C, sp2; O, sp3; HCO, ~120°

• C, sp2; O, sp2; HCO, ~120°

• C, sp2; O, sp2; HCO, ~109.5°

• C, sp3; O, sp2; HCO, ~109.5°

• C, sp3; O, sp3; HCO, ~109.5°

The double bond between carbon and oxygen is similar to an alkene C=C, except that C=O is

• shorter and weaker

• shorter and stronger

• longer and weaker

• longer and stronger

• longer

The positively polarized carbon atom of a carbonyl group acts as:

• an electrophile and a Lewis base

• a nucleophile and a Lewis base

• an electrophile and a Lewis acid

• a nucleophile and a Lewis acid

• both a Lewis acid and a Lewis base

Another name for β-methoxybutyraldehyde is:

• 2-methoxypropanal

• 3-methoxypropanal

• 2-methoxybutanal

• 3-methoxybutanal

• 2-methoxypentanal

Which of the following represents the correct ranking in terms of increasing boiling point?

• n-butane < 1-butanol < diethyl ether < 2-butanone

• n-butane < 2-butanone < diethyl ether < 1-butanol

• 2-butanone < n-butane < diethyl ether < 1-butanol

• n-butane < diethyl ether < 1-butanol < 2-butanone

• n-butane < diethyl ether < 2-butanone < 1-butanol

Which of the following compounds is most soluble in water?

• acetone

• cyclohexanone

• 2-butanone

• 3-butanone

• benzophenone

In carbon NMR, the carbon atom of the carbonyl group in aldehydes and ketones has a chemical shift of about:

• 20 ppm

• 40 ppm

• 60 ppm

• 120 ppm

• 200 ppm

Which compound will show an intense peak in the mass spectrum at m/z 58?

• CH3COCH2CH2CH3

• (CH3)2CHCOCH3

• CH3CH2COCH2CH3

• (CH3)3CCHO

• (CH3)3CCOCH3

n the mass spectrum of 3,3-dimethyl-2-butanone, the base peak will occur at m/z:

• 43

• 58

• 84

• 85

• 100

When a carbonyl is part of a conjugated π-network, the C=O stretch:

• has a higher frequency than in a nonconjugated system

• has a lower frequency than in a nonconjugated system

• always occurs at 1710 cm-1

• occurs around 2700 cm-1

• cannot be distinguished from the C=O stretch in a nonconjugated system