More NMR!
1) Which of the following compounds gives a DEPT-90 spectrum consisting of one
signal and a DEPT-135 spectrum consisting of three positive peaks and one
negative peak?
a) C(CH2CH3)4
b) (CH3)2CHCH(CH3)2
c) CH3CH2CH2CH3
d) (CH3)2CHCH2CH3
2) Propose a structure for a compound which has M+ = 86 in its mass spectrum, an
IR absorption at 3400cm-1, and the following 13C NMR spectral data:
Broadband decoupled 13C NMR: 30.2, 31.9, 61.8, 114.7, 138.4
DEPT-90: 138.4
DEPT-135: positive at 138.4; negative at 30.2, 31.9, 61.8, 114.7
C5H10O (1 degree of unsaturation)
HOCH2CH2CH2CH=CH2
3) Propose structures for compounds with the following formulas that show only one
peak in their 1H NMR spectra:
a. C5H12
(CH3)4C
b. C5H10
cyclopentane
c. C4H8O2
cyclohexane with 2 ether O’s across from each other
4) Propose a structure for C7H12O2, which has:
Broadband-decoupled 13C NMR: 19.1, 28.0, 70.5, 129.0, 129.8, 165.8
DEPT-90: 28.0, 129.8
DEPT-135: positive at 19.1, 28.0, 129.8; negative at 70.5, 129.0
H2C=CHCOOCH2CH(CH3)2
5) Draw a structure for C8H12O2
1
H NMR: 1.3 (12 H, singlet)
Broadband-decoupled 13C NMR: 215.42, 70.37, 18.82
IR: 1750 cm-1
6) Compound A, a hydrocarbon with M+ = 96 in its mass spectrum, has the 13C
spectral data that follow. On reaction with BH3 followed by treatment with basic
H2O2, A is converted into B, whose 13C spectral data are also given. Propose
structures for A and B.
Compound A:
Broadband-decoupled 13C NMR: 26.8, 28.7, 35.7, 106.9, 149.7
DEPT-90: no peaks
DEPT-135: negative peaks at 26.8, 28.7, 35.7, 106.9 (no positive)
Vinyl cyclohexane
Compound B:
Broadband-decoupled 13C NMR: 26.1, 26.9, 29.9, 40.5, 68.2
DEPT-90: 40.5
DEPT-135: positive at 40.5; negative at 26.1, 26.9, 29.9, 68.2
1-cyclohexyl-1-hydroxymethane
7)
a)
b)
c)
How many DEPT-90 signals will the above molecule have? 1
How many positive DEPT-135 signals? 2
How many negative DEPT-135 signals? 3