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Predict the approximate chemical shifts of the protons in
Chapter 18, Problem 35SP(choose chapter or problem)
Predict the approximate chemical shifts of the protons in the following compounds.
(a) benzene
(b) cyclohexane
(c) \(\mathrm{CH}_{3}-\mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Cl}\)
(d) \(\mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}\)
(f) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}-\mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\)
(h) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CHO}\)
Equation Transcription:
Text Transcription:
CH_{3}-O-CH_{2}CH_{2}CH_{2}Cl
CH_{3}CH_{2}-CC-H
CH_{3}CH_{2}-C-CH_{3}
(CH_{3})_{2}CH-O-CH_{2}CH_{2}OH
C-H
CH_{3}-CHCH-CHO
HO-CH_{2}CH_{2}-C-OCH(CH_{3})_{2}
Questions & Answers
QUESTION:
Predict the approximate chemical shifts of the protons in the following compounds.
(a) benzene
(b) cyclohexane
(c) \(\mathrm{CH}_{3}-\mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Cl}\)
(d) \(\mathrm{CH}_{3} \mathrm{CH}_{2}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}\)
(f) \(\left(\mathrm{CH}_{3}\right)_{2} \mathrm{CH}-\mathrm{O}-\mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{OH}\)
(h) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CHO}\)
Equation Transcription:
Text Transcription:
CH_{3}-O-CH_{2}CH_{2}CH_{2}Cl
CH_{3}CH_{2}-CC-H
CH_{3}CH_{2}-C-CH_{3}
(CH_{3})_{2}CH-O-CH_{2}CH_{2}OH
C-H
CH_{3}-CHCH-CHO
HO-CH_{2}CH_{2}-C-OCH(CH_{3})_{2}
ANSWER:
Solution 35SP
Chemical shift: The difference (in parts per million) between the resonance frequency of the proton being observed and that of tertamethylsilane (TMS).
(a) The structure of the benzene is shown below:
In benzene all the protons have the same chemical environment so all the protons have the same chemical shift. These are aromatic protons.
Hence, all the protons in benzene show the chemical shift value at 87.2.
(b) The structure of the cyclohexane is shown below:
In cyclohexane all the protons have the same chemical environment (at room temperature) so all the protons have the same chemical shift. These are alkyl protons.
Hence, all the protons in cyclohexane show the chemical shift value at 81.3.
(c) The structure of the compound is shown below:
This compound has four different types of protons. The protons which are attached to electronegative atoms have the more chemical shift values.
The chemical shift values for the compound as follows:
(d) The structure of the compound is shown below:
This compound has three different types of protons.
The chemical shift values for the compound as follows: