The following tables are 1H NMR and 13C NMR spectrum of cis-4-t-butylcyclohexano
ID: 998450 • Letter: T
Question
The following tables are 1H NMR and 13C NMR spectrum of cis-4-t-butylcyclohexanol and trans-4-t-butylcyclohexanol. According to the table, what are the relative proportions of the two isomeric products? What does that tell you about the mechanism of the reduction reaction and the stereochemistry of the starting material, products and intermediates?
1. cis-4-t-butylcyclohexanol
2. trans-4-t-butylcyclohexanol
1H NMR (400 MHz, CDCl3)
13C NMR (100 MHz, CDCl3)
Chemical shifts (ppm)
No. of hydrogens
Multiplicity
Assignment
Chemical shifts (ppm)
Assignment
3.5
1
Septet
HA
77.32
CDCl3
2.03
2
Doublet
HB
77.00
CDCl3
1.8
1
Singlet
HX
76.69
CDCl3
1.6
2
Doublet
HD
71.13
C1
1.22
2
Quartet
HC
47.12
C4
1.01
6
Doublet
HF
36.00
C2
0.92
3
Triplet
HE
32.23
C1
0.84
5
Singlet
HG
27.60
C2, C3, C4
25.55
C3
1H NMR (400 MHz, CDCl3)
13C NMR (100 MHz, CDCl3)
Chemical shifts (ppm)
No. of hydrogens
Multiplicity
Assignment
Chemical shifts (ppm)
Assignment
3.5
1
Septet
HA
77.32
CDCl3
2.03
2
Doublet
HB
77.00
CDCl3
1.8
1
Singlet
HX
76.69
CDCl3
1.6
2
Doublet
HD
71.13
C1
1.22
2
Quartet
HC
47.12
C4
1.01
6
Doublet
HF
36.00
C2
0.92
3
Triplet
HE
32.23
C1
0.84
5
Singlet
HG
27.60
C2, C3, C4
25.55
C3
H NMR 400MHZ CDCI 13c NMR (100 MHz, CDCl3) Chemical No of Multiplicity Assignment Chemical Assignment Chemical Shifts Shift (ppm) Hydrogens Shifts 13C NMR DEPT 0.86 Singlet -CH2 t-butyl methy 20.88 group 20.90 near to t-butyl Negative peak 0.95-1.02 Multiplate -CH3 -CH near of t-27.46 butyl group 27.48 t-butyl methyl group -CH2 of cycloxanol ring 1.29-1.55 Multiplate 32.53 Quaternary carbon of t butyl group Absent peak Axial-CH protons near to bulkyt butyl group 1.80-1.84 Multiplate 33.37 -CH2 33.39 Near of-OH group 4.02-4.04 Multiplate 48.01 Hydroxyl group -CH Near of t- 48.03 butyl group 65.87 -CH near to OH group 65.89Explanation / Answer
NMR technique is useful to estimate percentage of isomers when both the isomers are in same spectra. If a reaction yielded an unresolable isomers then the obtained H-NMR is comprises both the isomers peaks. then we can compare the area of peaks corresponding to both isomers resembles their isomeric percentage. Here, you are provided H-NMR and C-NMR of individual isomers. From individual isomeric spectra, we can not able to calculate isomeric percentage because comparision of prak intensities is not possible.
Isomeric product percentage of a particular reaction can be esimated analytically from thin layer chromatography and quantitatively by isolating products and their wieghts through column chromatography or by any other techniques (preparative TLC or quantitative HPLC).
Best wishes.
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