General Organic Chemistry

A carbocation is stable when it thes resonance, hyperconjugation, I effect.

In option (c), Benzylic carbocation (resonance with phenyl ring) and methyl group (hyperconjugation) lead to more stability.

Hydrogen bonding occurs when a molecule has a hydrogen atom bonded to a highly electronegative atom like N, O, or F — and there is a lone pair on another N, O, or F atom that can participate in bonding.

1. Ethanol (CH₃CH₂OH)

• Has an –OH group

✅ Can form hydrogen bonds (O–H···O)

2. Acetic acid (CH₃COOH)

• Has both C=O and –OH groups

✅ Forms strong hydrogen bonds (dimers, intramolecular and intermolecular H-bonding possible)

3. Ethylamine (CH₃CH₂NH₂)

• Has an –NH₂ group

✅ Can form hydrogen bonds (N–H···N or N–H···O with other molecules)

4. Trimethylamine ((CH₃)₃N)

• Has nitrogen with a lone pair but no N–H bond

❌ Cannot form H-bonds as donor, though it can accept them — but “having H‑bonding” typically means being capable of intermolecular H-bonding as both donor and acceptor. Since it cannot donate an H, we generally do not count it as hydrogen‑bonding on its own.

5. Salicylic acid (o-hydroxybenzoic acid)

• Has both –OH and –COOH groups; strong intramolecular hydrogen bond and intermolecular as well.

✅ H-bonding present

6. Ethanal (CH₃CHO)

• Has a C=O group only, no –OH or –NH–

❌ Cannot form hydrogen bonds with itself (can accept H bonds but not donate).

✅ Substances with H‑bonding:

1. Ethanol

2. Acetic acid

3. Ethylamine

4. Salicylic acid

Total = 4

✅ Correct Answer: Option A (4)

Toluene would be a suitable example of $X$ and nitrobenzene for $Y$.

In toluene, the methyl group CH bond can participate in hyperconjugation with the pi system of benzene ring.

Nitrobenzene exhibit resonance due to the interaction of the lone pair on the oxygen atom of the nitrogroup with the pi electrons of the benzene ring.

$ \text { The correct order of acidic strength is } $

Acidic character $\propto$ stability of conjugate base Stability of anion $\propto-M \propto-I$ effect and

$ \frac{1}{+I \text { effect }} \propto \frac{1}{\text { hyperconjugation }} $

A deactivating group attached to a benzene ring reduces the electron density within the ring, thereby slowing down and complicating electrophilic aromatic substitution reactions compared to reactions with benzene alone.

In the given list, the following are deactivating groups:

$-\mathrm{Cl}$

$-\mathrm{SO}_3\mathrm{H}$

$-\mathrm{COOCH}_3$

These groups withdraw electron density from the benzene ring, making it less reactive to electrophiles.

The electron withdrawing group increases the basicity while electron donating group decreases the basicity. So , the correct order is

$ B>A>C $

Nucleophiles are electron-rich species that donate an electron pair. In the given list:

$\mathrm{CH}_3 \mathrm{NH}_2$ (methylamine): This compound contains a nitrogen atom with a lone pair of electrons, making it an effective nucleophile.

$\mathrm{CH}_3 \mathrm{SH}$ (methanethiol): The sulfur atom in this molecule also has a lone pair of electrons, allowing it to act as a nucleophile.

On the other hand, electrophiles are electron-deficient species that can accept an electron pair. In the list:

$\mathrm{CH}_3 \mathrm{CHO}$ (acetaldehyde): This compound is an electrophile because the carbonyl carbon is electron-deficient and can accept electron pairs.

Lastly:

$\mathrm{C}_2 \mathrm{H}_4$ (ethylene): This acts as a substrate and is not typically considered a nucleophile.

Therefore, the number of nucleophiles in the list is two: $\mathrm{CH}_3 \mathrm{NH}_2$ and $\mathrm{CH}_3 \mathrm{SH}$.

Tropolone is an example of non-benzenoid aromatic compound.

Tropolone is an organic compound that is pale yellow in colour. It is a seven-membered cyclic ring.

The following three compound shows negative resonance $(-R)$ effect when attached to conjugate system. $A \rightarrow$ formyl, $D \rightarrow$ cyano, $E \rightarrow$ nitro. The negative resonance effect occurs when the groups withdraw the electrons from other molecules by delocalisation process.

The acidity of compound depends upon the strength of electron withdrawing group present in it. The order of $+I$ effect (electron withdrawing effect) is

$ \mathrm{NO}_2>\mathrm{CN}>\mathrm{F} $

Hence, the order of acidity is

Electron rich groups act as ortho and para directing groups as they increases electron density at these two positions.

Out of the given groups, following are electron rich and deficient,

Electron rich $-\mathrm{OH},-\mathrm{OCH}_3,-\mathrm{NHCOCH}_3$

Electron deficient $-\mathrm{CN},-\mathrm{CO}_2 \mathrm{H},-\mathrm{CHO}$

Hence, $-\mathrm{OH},-\mathrm{OCH}_3$ and $-\mathrm{NHCOCH}_3$ acts as ortho and para-directing groups towards electrophilic substitution reactions.

is not an aromatic compound as it has only 4$\pi$ electrons. So, it follows 4n $\pi e^-$ rule, which makes it anti-aromatic compound.

$\mathrm{p} K_b \propto \frac{1}{\text { Basicity }}$

$A$ and $B$ are more basic than $C$ and $D$ due to $+I$-effect of methyl group $A$ which is more basic than $B$. This is because of high/more steric hindrance in $B$ due to three methyl groups. Out of $C$ and $D, C$ is more basic than $D$ because of more steric hindrance in $B$. So, order of basicity is

Thus, decreasing pK_b order of given compounds is

i.e. D > C > B > A.

Methoxybenzene in the presence of anhydrous aluminium chloride (anhyd. AlCl$_3$) reacts with ethanoyl chloride to form 2-methoxy acetophenone and 4-methoxy acetophenone which is further converted to 4-ethyl phenol.

The most reactive towards electrophilic reagent is $o$-cresol.

The phenolic $(-\mathrm{OH})$ group increases the electron density on benzene ring through resonance. With increase in electron density, the reactivity towards electrophilic reagent increases. The decreasing order of activating influence of substituents towards electrophilic reagent is

$\begin{aligned} & \mathrm{NR}_2>-\mathrm{NH} R>-\mathrm{NH}_2>-\mathrm{OH}>-\mathrm{OR}> \\ & -\mathrm{NHCOR}>-\mathrm{ph}>-R \end{aligned}$

Hyperconjugation is a stabilising interaction between one or more $\sigma$-bonds and one or more $\pi$-bonds.

It helps in explaining stability order of free radicals, carbocations, alkanes but cannot explain stability of carbanion due to presence of vacant orbitals.

According to Markownikov rule, in addition reaction of unsymmetrical alkenes, electron rich component of reagent add to carbon atom with fewer hydrogen atoms bonded to it.

The complete shifting of $\pi$-electron pair of a multiple bond to one of the bonded atoms in presence of the attacking reagents is called electromeric effect.

Positive electromeric effect (+E)

Negative electromeric effect [$-$E]

In positive $+$E effect, $\pi$-electrons of the multiple bonds are transfered to that atom to which the reagent gets attached.

In negative $-$E effect, $\pi$-electrons of the multiple bonds are transferred to that atom to which the attacking reagent does not get attached.