Organic Chemistry Basics - Result Question 69
####21. The IUPAC name of the compound
$CH _2=CH-CH\left(CH _3\right) _2$ is
(1987, 1M)
(a) 1,1-dimethyl-2-butene
(b) 3-methyl-1-butene
(c) 2-vinyl propane
(d) None of these
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Answer:
Correct Answer: 21. (d)
Solution:
- A mono-substituted benzoic acid is stronger than a mono-substituted phenol as former being a carboxylic acid. Among the given substituted benzoic acid, ortho-hydroxy acid is strongest acid although $-OH$ causes electron donation by resonance effect which tends to decrease acid strength.
It is due to a very high stabilisation of conjugate base by intramolecular $H$-bond which outweigh the electron donating resonance effect of $-OH$.
The overall order of acid-strength of given four acids is ortho-hydroxybenzoic acid $\left(p K _a=2.98\right)>$ Toluic acid $\left.p K _a=4.37\right)>p$-hydroxybenzoic acid $\left(p K _a=4.58\right)>$ $p$-nitrophenol $\left(p K _a=7.15\right)$
