Arrange the following in decreasing order of their acidic strength. Give explanation for the arrangement.
$$\mathrm{C}_6 \mathrm{H}_5 \mathrm{COOH}, \mathrm{FCH}_2 \mathrm{COOH}, \mathrm{NO}_2 \mathrm{CH}_2 \mathrm{COOH}$$
The decreasing order of their acidic strength
$$\mathrm{NO}_2 \mathrm{CH}_2 \mathrm{COOH}>\mathrm{FCH}_2 \mathrm{COOH}>\mathrm{C}_6 \mathrm{H}_5 \mathrm{COOH}$$
Acidic strength decreases as the number of electron withdrawing substituent(s) linked to $\alpha$-carbon atom or carboxylic group of carboxylic acid decreases. Electron withdrawing ability of $\mathrm{NO}_2, \mathrm{~F}$ and $\mathrm{C}_6 \mathrm{H}_5$ are as follows
$$-\mathrm{NO}_2>-\mathrm{F}>\mathrm{C}_6 \mathrm{H}_5-$$
but alkenes show electrophilic addition reactions whereas carbonyl compounds show nucleophilic addition reactions. Explain.
Nature of chemical reaction occurring on $>\mathrm{C}=\mathrm{C}<$ bond or $>\mathrm{C}=\mathrm{O}$ bond can be explained on the basis of nature of bond between $>\mathrm{C}=\mathrm{C}<$ and $>\mathrm{C}=\mathrm{O}$.
Thus, in $>\mathrm{C}=\mathrm{O}$ carbon acquires partially positive charge and O acquires partially negative charge and show nucleophilic addition reaction to the electrophilic carbonyl carbon. On the other hand, $>\mathrm{C}=\mathrm{C}<$ undergo electrophilic addition reaction due to nucleophilic nature of $>\mathrm{C}=\mathrm{C}<$ which contains $\pi$ bond.
Carboxylic acids contain carbonyl group but do not show the nucleophilic addition reaction like aldehydes or ketones. Why?
Carboxylic acid contain carbonyl group but do not show nucleophilic addition reaction like aldehyde and ketone. Due to resonance as shown below the partial positive charge on carbonyl carbon atom is reduced.
Identify the compounds A, B and C in the following reaction.
$\mathrm{CH}_3-\mathrm{Br} \xrightarrow{\text { Mg/ether }}[A] \xrightarrow[\text { (i) Water }]{\text { (i) } \mathrm{CO}_2}[B] \xrightarrow[\Delta]{\mathrm{CH}_3 \mathrm{OH} / \mathrm{H}^{+}}[C]$
Complete chemical conversion can be done as
Why are carboxylic acids more acidic than alcohols or phenols although all of them have hydrogen atom attached to a oxygen atom ( $-0-\mathrm{H}$ )?
Carboxylic acids are more acidic than alcohol or phenol, although all of them have $\mathrm{O}-\mathrm{H}$ bond. This can be explained on the basis of stability of conjugate base obtained after removal of $\mathrm{H}^{+}$from acid or phenol.
Hence, dissociation of $\mathrm{O}-\mathrm{H}$ bond in case of carboxylic acid become easier than that of phenol. Hence, carboxylic acid are stronger acid than phenol.