Question

(a) Write the resonance structure of carboxylic acid derivative `(R-underset(O)underset(||)(C)-G)` and account for the stability and electrophilic character of the `(C=O)` group.
(b) Why is the `(C-G)` bond in the acid derivative shorter and stronger than the `(R-G)` bond in alkyl derivative ?
( c) Write the eclipsed configuration structures for `N-methyl` ethanamide about the `(C-N)` bond.

Answer 1

(a)
The `EDG` from `G` to `O` stabilities `(C==O)`, thereby decreasing the electrophilic character of `C`.
(b) In `(R-overset(O)overset(||)(C)-G), C` of `(C=O)`group is `sp^2-hybridised` with `G`, while `C` in `(R-G)(R-Cl , R-NH_2, R-OH R-OR`, etc) is `sp^3-hybridised`. In `sp^2`, the s-character is more than that in `sp^3`, which makes the `(C-G)` bond in acid derivatives shorter and stronger than the `(R-G)` bond in alkyl derivative. The dipolar hybrid structure `(IV)` with a partial double bond between `(C and G)` is also responsible for these bond properties.
c. `(Me-overset(O)overset(||)(C)-NH-Me)` (N-Methyl ethanamide or N-methyl acetamide).
It exists in two eclipsed configuration structures, i.e., `E-` and `Z-forms`. Although they are not isolable at room `E-` and `Z-forms`. Althrough they ar not isolable at room `E-` and `Z-forms`. Although they are not isolable at room temperature, they can be detected by spectroscopic methods.
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