# NEET Chemistry Reaction Mechanism - Organic Chemistry Questions Solved

Reactivity order of halides for dehydrohalogenation is

(a) R-F>R-Cl>R-Br>R-I(b) R-I>R-Br>R-Cl>R-F(c) R-I>R-Cl>R-Br>R-F(d) R-F>R-I>R-Br>R-Cl

(b) F,Cl,Br and I are the elements of VII A group. In a group atomic radii increases from top to bottom and the bond dissociation energy decreases as

R-F>R-Cl>R-Br>R-I

So, during dehydrohalogenation R-I bond breaks more easily than R-I bond. Hence, order of reactivity will be

R-I>R-Br>R-Cl>R-F

Difficulty Level:

• 32%
• 55%
• 12%
• 3%

The increasing order of hydrolysis of the following compounds:

(a) (i)<(iii)<(ii)

(b) (ii)<(iii)<(i)

(c) (ii)<(i)<(iii)

(d) (i)<(ii)<(iii)

(a) Higher is the stability of intermediate (carbocation), more is the reactivity of compound.

(ii) forms allyl carbocation, (iii) forms secondary  carbocation and (i) forms phenyl carbocation.

Difficulty Level:

• 28%
• 22%
• 10%
• 42%

What is major product of following reaction ?

(3) Dehydrohalogenation is an example of anti elimination.

Dehydrohalogenation: A reaction in which a hydrogen atom and a halogen atom are removed from adjacent atoms in a molecule, forming (usually) an alkene or an alkyne.

When reacted with strong base such as hydroxide ioncyclohexyl chloride suffers dehydrohalogenation by a concerted E2 reaction mechanism (shown here). The atoms which comprise the moleculeof HCl lost are shown in red. This reaction is the conceptual reverse of electrophilic addition of HCl to cyclohexene.

tertiary alkyl halide such as 2-iodo-2-methylpropane can undergo dehydrohalogenation by the E1 reaction mechanism (shown here). The atoms which comprise the molecule of HI lost are shown in red.

When reacted with a strong base such as sodium amide (NaNH2), a geminal dibromide can undergo a double dehydrohalogenation reaction to give an alkyne. The reaction involves a pair of consecutive E2 elimination steps.
•

Difficulty Level:

• 20%
• 49%
• 27%
• 6%

Difficulty Level:

• 20%
• 33%
• 29%
• 20%

Consider the given reaction below:

Which of these is true regarding the reaction shown above?

(1) the configuration of the chiral carbon remains same.

(2) the configuration of the chiral carbon gets inverted

(3) the  compound formed as a product must be a dextro isomer

(4) the reactant is optically inactive but the product is obtained as a levo isomer.

(1) the configuration of the chiral carbon remains same because the priority of CN- and -COOH is same.

Difficulty Level:

• 57%
• 17%
• 16%
• 12%

$\underset{∆}{\overset{\mathrm{Zn}}{\to }}$ A$\underset{{\mathrm{NH}}_{3}/\mathrm{EtOH}}{\overset{\mathrm{Na}}{\to }}$ B

Product 2 is

(1)

Difficulty Level:

• 28%
• 27%
• 38%
• 9%

(1) the ease of dehydrohalogenation of alkyl halide is: $3°>2°>1°$

Difficulty Level:

• 71%
• 22%
• 6%
• 3%

Which of the following is formed by the thermal decomposition of the hydroxide of:

It is an example of Hoffman elimination

Difficulty Level:

• 25%
• 33%
• 20%
• 23%

(1) Both the ethers obtained by the two routes have opposite but equal optical rotation.

(2) One of the ether is obtained as a racemic mixture.

(3) Step II & III both are SN2 reaction and both have inversion.

(4) Step II has inversion but step III has retention.

(1)

Difficulty Level:

• 32%
• 29%
• 30%
• 11%

P is

(1) Ph–O–SO2OMe

(2) PhOMe

(3) PhOSO2OPh

(4) PhMe

(2)

Difficulty Level:

• 31%
• 51%
• 11%
• 9%