18) In carbon NMR, the carbon atom of the carbonyl group in aldehydes and ketones has a chemical shift of about:
A) 20 ppm.
B) 40 ppm.
C) 60 ppm.
D) 120 ppm.
E) 200 ppm.
E) 200 ppm.
19) In the proton NMR spectra of aldehydes and ketones, the protons bonded to carbons adjacent to the carbonyl group typically fall into which of the chemical shift ranges below?
A) 1.0-2.0 ppm
B) 2.0-3.0 ppm
C) 4.0-4.5 ppm
D) 7.0-8.0 ppm
E) 9.0-10.0 ppm
B) 2.0-3.0 ppm
20) The proton NMR spectrum of an unknown compound contains a triplet at 9.8 ppm. Which of the following could be this unknown?
A) (CH3)3CCHO
B) CH3CH2CH2CO2H
C) CH3CH2CH2CHO
D) CH3CO CH2Ph
E) PhCHO
C) CH3CH2CH2CHO
38) When the carbonyl group of a neutral ketone is protonated,:
A) the resulting species becomes more electrophilic.
B) the resulting species is activated toward nucleophilic attack.
C) subsequent nucleophilic attack on the resulting species is said to oc
E) all of the above.
57) What intermediate occurs when a ketone undergoes a Wolff-Kishner reduction?
A) a cyanohydrin
B) a hydrated aldehyde
C) a carboxylate
D) a semicarbazone
E) a hydrazone
E) a hydrazone
58) Which would be more appropriate as the reduction in the following sequence, a Clemmensen or
a Wolff-Kishner? Explain.
Answer: Wolff-Kishner. The acidic conditions of the Clemmensen would remove the protecting group causing reduction of the aldehyde as
Wolff-Kishner. The acidic conditions of the Clemmensen would remove the protecting group causing reduction of the aldehyde as well.
Diff: 3
59) The reagent which converts a carbonyl group of a ketone into a methylene group is:
A) Na, NH3, CH3CH2OH
B) LiAlH4
C) NaBH4, CH3CH2OH
D) Zn(Hg), conc. HCl
E) LiAlH[OC(CH3)3]3
D) Zn(Hg), conc. HCl
74) Which of the following compounds would show only one triplet in its off resonance decoupled 13C NMR spectrum?
A) acetone
B) butanal
C) pentanal
D) 2-pentanone
E) 3-pentanone
E) 3-pentanone
76) Oxidation of a 1� alcohol with chromic acid results in the production of __________.
A) an ester
B) a ketone
C) an aldehyde
D) an ether
E) none of the above
E) none of the above
77) Oxidation of a 2� alcohol with chromic acid results in the production of __________.
A) an ester
B) a ketone
C) an aldehyde
D) an ether
E) none of the above
B) a ketone
78) Oxidation of a 3� alcohol with chromic acid results in the production of __________.
A) an ester
B) a ketone
C) an aldehyde
D) an ether
E) none of the above
E) none of the above
79) Oxidation of a 1� alcohol with pyridinium chlorochromate results in the production of __________.
A) an ester
B) a ketone
C) an aldehyde
D) an ether
E) none of the above
C) an aldehyde
80) Treatment of a nitrile with a Grignard reagent followed by hydrolysis results in __________.
A) an ester
B) a ketone
C) an aldehyde
D) an ether
E) an alcohol
B) a ketone