solve part b 20 14. The NMR spectrum of propanol is shown. Chem. Rel. expanded v
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solve part b
20 14. The NMR spectrum of propanol is shown. Chem. Rel. expanded views shift area 0.93 3.00 1.56 2.00 3.17 1.00 3.58 2.00 (b) TMS CH3 CH2CH2OH (d) (c) (a) 0 ppm Chemical shift (6) a) Match the protons in the molecule to the corresponding peaks in the spectrum. Explain how you come to your conclusions. (base your explanation on the spin-spin splitting and your understanding of chemical shifts). (6 pts) b) Explain why the peak at 3.58 6 is shifted farthest downfield? (4 pts) c) What is the purpose of the TMS peak? (4 pts) d) In NMR why, in terms of magnet strength, is bigger better? (4 pts)Explanation / Answer
ANS 14 B)
1) Proton shifts move downfield when electromagnetic substituents are attached to the same or a adjacent carbon.here in CH3CH2CH2OH ,The electronegativity of OH is very much higher than the carbon sp2 groups attached. 3.58 shows the peak of OH, which is making a triplet AT 3.58.
2)The peak of 0.93 depict CH3, the peak of 1.56 depict CH2 and 1.76 depict CH2 adjacent to the OH is a little downfield.
3) Also in OH we can see a hydrogen bonding that suggest a large shift in values,the more the hydrogen bonding ,the more the proton is deshielded and more or higher the chemical shift will be . since amount of hydrogen bonding depends on number of factors like sovation, acid character so its usefull to assign the value of (OH and NH ) after rest of the groups has been assigned.
4) When there is more electronegative atom,the electron density is less, which makes the proton shift downfield.
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