Haloalkanes and Haloarenes Test

Result

Haloalkanes and Haloarenes Test - 28

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Weekly Quiz Competition

Question 1
1 / -0

$$C_6H_5-\!\!\!\!\!\underset{H}{\underset{|}{\overset{\,\,\,\,\,\,CH_3}{\overset{|}{C}}}}\!\!\!\!\!-Br+H_2O \to HO -\!\!\!\!\!\underset{H}{\underset{|}{\overset{\,\,\,\,\,\,CH_3}{\overset{|}{C}}}}\!\!\!\!\! -C_6H_5+HBr$$

The above reaction result in 98% racemization, the reaction mainly follows:

A
$$S_{N}1$$ mechanism

B
$$S_{N}2$$ mechanism

C
$$E^{1}$$ mechanism

D
$$E^{2}$$ mechanism

Solution

An alkyl halide with chiral carbon forms a racemic mixture through $$SN^1$$ mechanism.

$$SN^2$$ mechanism changes the configuration of a compound due to formation of the transition state.

$$SN^1$$ mechanism proceeds through carbocation formation so it's a two-step process and as stability of carbocation increases, reaction favours $$SN^1$$ mechanism.

$$3^0$$ carbocation are more stable than others and also polar solvent increases the stability of carbocation so they both favours $$SN^1$$ mechanism.

Also, the rate of $$SN^1$$ mechanism depends on nucleophile concentration only so as conc. of nucleophile increases, reaction favours $$SN^1$$ mechanism.
Question 2
1 / -0

Which of the following statement is not correct?

A
Chlorobenzene is more reactive than benzene towards electrophilic substitution

B
$$C- Cl$$ bond in chlorobenzene is less polar than $$CH Cl_{3}$$

C
Chlorobenzene is less reactive than $$CH Cl_{3}$$

D
In chlorobenzene further substitution takes place at ortho and para positions

Solution

$$Chlorine$$ shows two effects $$-I$$ & $$+M$$.

Due to$$ the - I $$ effect of $$Cl$$ group, it reduces the electron density of benzene so chlorobenzene is less reactive than benzene for electrophilic substitution reaction.

But due to the $$+M$$ effect, it is ortho, para directing, and in chlorobenzene further substitution takes place at ortho and para positions.

Option A is correct.
Question 3
1 / -0

The compound $$X$$ is:

A
o-methylchlorobenzene

B
p-methylchlorobenzene

C
m-methylchlorobenzene

D
both $$A$$ & $$B$$

Solution

As $$Cl-$$ group attached to benzene is ortho, para directing so it forms $$o-,p-$$ chloro toluene.

Reaction is as shown.
Question 4
1 / -0

Which of these is o, p-directing and deactivating group?

A
$$-F$$

B
$$-Cl$$

C
$$-Br$$

D
All of these

Solution

$$X-$$ (halogen group) has two effects $$-I$$ & $$+M$$.

Due to the $$-I$$ group, it reduces the electron density of benzene so halobenzene is less reactive than benzene for electrophilic substitution reaction.

But due to the $$+M$$ effect, it is ortho, para directing (resonance effect predominates over inductive effect) and in halobenzene, further substitution takes place at ortho and para positions.
Question 5
1 / -0

If $$C_{4}H_{9}Cl$$ with $$Na/ether$$ gives $$2,5$$-dimethylhexane, then the compound, $$C_{4}H_{9}Cl$$ is:

A
n-butylchloride

B
sec-butylchloride

C
iso-butylchloride

D
tert-butylchloride

Solution

The reaction of Isobutyl chloride $$(C_{4}H_{9}Cl)$$ with $$Na/Ether$$ gives $$2,5$$-dimethylhexane. This is a condensation reaction in which two molecules of sodium chloride are obtained for every molecule of $$2,5$$-dimethylhexane.

Option C is correct.
Question 6
1 / -0

The reaction of toluene with $$Cl_{2}$$ in presence of $$Fe$$, the product(s) formed is/are:

A
o- and p-chlorotoluene

B
benzyl chloride

C
m-chlorotoluene

D
only p-chlorotoluene

Solution

$$-CH_3$$ group on benzene is ortho and para directing.

In presence of $$Cl^-$$, it forms ortho (minor) and para (major) chlorotoluene as products.

Option A is correct.
Question 7
1 / -0

Which one of the following compounds is most reactive for aromatic electrophilic substitution reaction?

A
$$C_{6}H_{5}-F$$

B
$$C_{6}H_{5}-Cl$$

C
$$C_{6}H_{5}-I$$

D
$$C_{6}H_{5}-NO_{2}$$

Solution

Due to $$- I$$ effect of $$X-$$ group, it reduces electron density of benzene, so halobenzene is less reactive than benzene for electrophilic substitution reaction.

As electro-negativity of $$F$$ is highest among halogens, so its $$-I$$ effect is highest.

So, reactivity of halobenzene compounds towards electrophilic substitution is $$ Ph-I > Ph-Cl >Ph-F$$.

Due to $$-M$$ effect of nitrate group, it is less reactive than other compounds.

Option C is correct.
Question 8
1 / -0

Which of the following is used in paint removing?

A
$$CHCl_{3}$$

B
$$CH_{2}Cl_{2}$$

C
$$CCl_{4}$$

D
$$CH_{3}Cl$$

Solution

$$CHCl_3$$ is used as solvent and as an anaesthetic.
$$CCl_4$$ is used as a fire extinguisher.
$$CH_2Cl_2$$ is used as paint removing.
$$CH_3Cl$$ is used as a refrigerant.

Hence, the correct option is B.
Question 9
1 / -0

$$2C_{6}H_{5}Cl+2Na\rightarrow X$$
In the given reaction $$X$$ is:

A
toulene

B
biphenyl

C
phenyl ethane

D
$$1$$-chloro-$$2$$-phenyl ethane

Solution

Fitting reaction: Aryl chloride reacts with Na in presence of dry ether and diaryl forms as product.(similar to Wurtz reaction).
Reaction:
$$2C_{6}H_{5}Cl+2Na\rightarrow Ph-Ph+2NaX$$
Question 10
1 / -0

Reaction of Chlorobenzene with $$CH_3Cl$$ in presence of $$AlCl_{3}$$ gives:

A
Toulene

B
m-chloro toulene

C
Only o-chloro toulene

D
Mixture of o- and p-chlorotoulene

Solution

As $$Cl^-$$ group attached to benzene is ortho, para directing so it forms $$o-,p-$$ chloro toluene.
This is a Fridel Craft's alkylation reaction.