HNMR of methylcyclohexanol 1) 2-Methycyclohexanol is prepared commercially by ca
ID: 937958 • Letter: H
Question
HNMR of methylcyclohexanol
1) 2-Methycyclohexanol is prepared commercially by catalytic hydrogenation of ocresol (2-methylphenol) and consists of a mixture of cis and trans isomers. (Note the spectrum is for the mixture.) (Hint: What do the peaks at 3.05 ppm and 3.75 ppm represent and what does their integration show?)
b. Describe how you can determine the ratio of cis- and trans-2- methylcyclohexanols from the 1 H NMR spectrum provided.
c. Which peak between 3-4 ppm belongs to trans-2-methylcyclohexanol? 3.05 ppm or 3.75 ppm?
2-METHYLCYCLOHEXANOL MIXTURE OF CIS AND TRANS ISOMERS GE QE- 111991 19NOVS 2-METHYL-CYCL OPERATOR: JO ONE PULSE SE PULSE WIDTH ACQ. TIME RECYCLE TIME NO. OF ACQS DATA SIZE LINE BROADN SPIN RATE OBSERVE FREQUENCY SPEC WIDT GAIN 4. 0 3.8 3. 6 3.4 3.2 3.0 2 4.0 3.8 3.6 3. 4 3. 2 3.0 2.8 PPM PLOT SCALE 60 FROM TO PEAK LIS HT 4 10 8 19 9 18 4 2 PPMExplanation / Answer
a) From the integration value ration we can find the Cis-, trans- percentage (here integration values are not mentioned).
b) the ratio of cis and trans-2-methylcyclohexanol can be determined by the signal intensity of chemical shift of hydrogen atom on methyl group.
c) hydroxyl group is an electron-withdrawing group. As a result, the hydrogen atoms near hydroxyl group will be deshielding.
however sheilding constant (sigma) has a strong relationship with distance.
hydrogen atoms on methyl group of trans-2-methylcyclohexanol have longer distance than cis one, and the signal of hydrogen atoms on methyl group will shift to downfield.
trans-2-methylcyclohexanol having a value of 3.75 ppm
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