Q: How will you convert:(i) Propene to propan\$-1-\$ol? (ii) Ethanal to propan-2-ol?

(i) \$\underset{propene}{CH_3CH=CH_2} + HBr \xrightarrow {peroxide} CH_3CH_2CH_2Br + KOH(aq) \xrightarrow {\Delta} \underset{propan-1-ol}{CH_3CH_2CH_2OH}\$(ii) \$\underset{Ethanal}{CH_3CH=O} \xrightarrow {CH_3MgI} CH_3CH(OMgI)CH_3 \xrightarrow {H^+,H_2O} \underset{propan-2-ol}{CH_3CH(OH)CH_3}\$

Q: Explain the preparation of phenol from cumene.

Preparation of phenol from cumene \$\rightarrow\$To prepare phenol, cumene is first oxidised in the presence of air to cumene hydroperoxide.\$\underset{\left( \text{Isoprophyl benzene} \right)}{\text{Cumene}} \xrightarrow[]{{O}_{2}} \text{Cumene hydroperoxide}\$Now, cumene hydroperoxide is treated with dilute acid to prepare phenol and acetone as by-products.\$\text{Cumene hydroperoxide} \xrightarrow[323-363 \; K]{{H}^{+}} \text{Phenol} + \text{Acetone}\$By this method, acetone is obtained in large quantities.

Q: \$C_{6}H_{5}NH_{2}\xrightarrow{NaNO_{2}+HCl,\: 0^{o}C}X {\xrightarrow{H_{2}O,\: warm}}Y\$In the above reaction, \$Y\$ is:

\$C_6H_5NH_2\$ gives benzene diazonium chloride (\$X\$) upon reaction with \$NaNO_2\$ and \$HCl\$. The formed benzene diazonium chloride (\$X\$) gives phenol (\$Y\$) in the presence of water.The reaction is as follows:Option C is correct.

Question 1

How will you convert:(i) Propene to propan$-1-$ol?  (ii) Ethanal to propan-2-ol?

Accepted Answer

(i) $\underset{propene}{CH_3CH=CH_2} + HBr \xrightarrow {peroxide} CH_3CH_2CH_2Br + KOH(aq) \xrightarrow {\Delta} \underset{propan-1-ol}{CH_3CH_2CH_2OH}$(ii) $\underset{Ethanal}{CH_3CH=O} \xrightarrow {CH_3MgI} CH_3CH(OMgI)CH_3 \xrightarrow {H^+,H_2O} \underset{propan-2-ol}{CH_3CH(OH)CH_3}$

Question 2

Explain the preparation of phenol from cumene.

Accepted Answer

Preparation of phenol from cumene $\rightarrow$To prepare phenol, cumene is first oxidised in the presence of air to cumene hydroperoxide.$\underset{\left( \text{Isoprophyl benzene} \right)}{\text{Cumene}} \xrightarrow[]{{O}_{2}} \text{Cumene hydroperoxide}$Now, cumene hydroperoxide is treated with dilute acid to prepare phenol and acetone as by-products.$\text{Cumene hydroperoxide} \xrightarrow[323-363 \; K]{{H}^{+}} \text{Phenol} + \text{Acetone}$By this method, acetone is obtained in large quantities.

Question 3

An alkene $CH_3CH = CH_2$ is treated with $B_2H_6$ in presence of $H_2O_2$. The final product formed is:

Accepted Answer

Hydroboration-oxidation reaction follows anti-Markovnikov's addition of $H-OH$ across $C=C$ to give alcohol.Thus an alkene $CH_3CH=CH_2$ when treated with $B_2H_6$ in presence of $H_2O_2$ will yield the final product as  $CH_3CH_2CH_2OH$

Question 4

Write the mechanism of hydration of ethene to yield ethanol.

Accepted Answer

Three steps are involved in the mechanism of hydration of ethene to yield ethanol.$(1)$ The electrophillic attack of hydronium ion protonates ethene to form carbocation.$(2)$ Water (as a nucleophile) attacks carbocation.$(3)$ Deprotonation gives ethanol.The mechanism is shown above.

Question 5

Chlorination of toluene in presence of light and heat followed by treatment with aqueous NaOH gives:

Accepted Answer

Chlorination of toulene in presence of light and heat followed by treatment with aqueous $NaOH$ gives Benzoic acid.

Question 6

$C_{6}H_{5}NH_{2}\xrightarrow{NaNO_{2}+HCl,\: 0^{o}C}X {\xrightarrow{H_{2}O,\: warm}}Y$In the above reaction, $Y$ is:

Accepted Answer

$C_6H_5NH_2$ gives benzene diazonium chloride ($X$) upon reaction with $NaNO_2$ and $HCl$. The formed benzene diazonium chloride ($X$) gives phenol ($Y$) in the presence of water.The reaction is as follows:Option C is correct.

Question 7

What is meant by hydroboration-oxidation reaction? Illustrate it with an example.

Accepted Answer

Hydroboration-oxidation reaction is the addition of borane followed by oxidation. For example, propene on hydroboration-oxidation gives propan-$1$-ol.The reaction of propene with diborane gives trialkyl borane as an addition product.Oxidation by hydrogen peroxide in presence of aqueous sodium hydroxide gives propan-$1$-ol.

Question 8

In the following sequence of reactions$CH_3CH_2CH_2Br \overset{KOH(alc)}{\longrightarrow} (A) \overset{HBr}{\longrightarrow} (B) \overset{KOH (aq.)}{\longrightarrow} (C).$The product (C) is

Accepted Answer

Toppr Ask Answer

Question 9

How is phenol prepared from Benzene Sulphonic acid?

Accepted Answer

Benzene sulphonic acid is initially treated with an aqueous solution of $NaOH$. It is then mixed with solid $NaOH$ and fused at high temperature. The resulting product is then acidified to yield phenol. The entire process has been schematically shown above.

Question 10

Predict the product of the following reaction?

Accepted Answer

Option C is the correct answer.This is Wittig's reaction and we obtain an alkene as the final product as shown in the mechanism.

Revise with Concepts

Preparation Methods of Alcohols - from Alkenes

Preparation Methods of Alcohols - From Primary Amine, Alkyl Halide, Carbonyl Compounds and Grignard Reagents

Preparation Methods of Phenol

Quick Summary With Stories

Preparation Methods of Alcohols - from Alkenes

Preparation of alcohols: Hydroboration-oxidation

Preparation Methods of Alcohols - from Carbonyl Compounds

Preparation of Alcohols from Grignard Reagent

Preparation of Phenols

How will you convert:
(i) Propene to propan $- 1 -$ ol?
(ii) Ethanal to propan-2-ol?

Explain the preparation of phenol from cumene.

An alkene $C H_{3} C H = C H_{2}$ is treated with $B_{2} H_{6}$ in presence of $H_{2} O_{2}$ . The final product formed is:

Write the mechanism of hydration of ethene to yield ethanol.

Chlorination of toluene in presence of light and heat followed by treatment with aqueous NaOH gives:

$C_{6} H_{5} N H_{2} N a N O_{2} + H C l, 0^{o} C X H_{2} O, w a r m Y$

In the above reaction, $Y$ is:

What is meant by hydroboration-oxidation reaction? Illustrate it with an example.

In the following sequence of reactions
$C H_{3} C H_{2} C H_{2} B r ⟶ K O H (a l c) (A) ⟶ H B r (B) ⟶ K O H (a q .) (C) .$
The product (C) is

How is phenol prepared from Benzene Sulphonic acid?

Predict the product of the following reaction?

Revise with Concepts

Preparation Methods of Alcohols - from Alkenes

Preparation Methods of Alcohols - From Primary Amine, Alkyl Halide, Carbonyl Compounds and Grignard Reagents

Preparation Methods of Phenol

Quick Summary With Stories

Preparation Methods of Alcohols - from Alkenes

Preparation of alcohols: Hydroboration-oxidation

Preparation Methods of Alcohols - from Carbonyl Compounds

Preparation of Alcohols from Grignard Reagent

Preparation of Phenols

How will you convert:(i) Propene to propan−1−ol? (ii) Ethanal to propan-2-ol?

Explain the preparation of phenol from cumene.

An alkene CH3​CH=CH2​ is treated with B2​H6​ in presence of H2​O2​. The final product formed is:

Write the mechanism of hydration of ethene to yield ethanol.

Chlorination of toluene in presence of light and heat followed by treatment with aqueous NaOH gives:

C6​H5​NH2​NaNO2​+HCl,0oC​XH2​O,warm​Y In the above reaction, Y is:

What is meant by hydroboration-oxidation reaction? Illustrate it with an example.

In the following sequence of reactions CH3​CH2​CH2​Br⟶KOH(alc)​(A)⟶HBr​(B)⟶KOH(aq.)​(C). The product (C) is

How is phenol prepared from Benzene Sulphonic acid?

Predict the product of the following reaction?

How will you convert:
(i) Propene to propan $- 1 -$ ol?
(ii) Ethanal to propan-2-ol?

An alkene $C H_{3} C H = C H_{2}$ is treated with $B_{2} H_{6}$ in presence of $H_{2} O_{2}$ . The final product formed is:

$C_{6} H_{5} N H_{2} N a N O_{2} + H C l, 0^{o} C X H_{2} O, w a r m Y$

In the above reaction, $Y$ is:

In the following sequence of reactions
$C H_{3} C H_{2} C H_{2} B r ⟶ K O H (a l c) (A) ⟶ H B r (B) ⟶ K O H (a q .) (C) .$
The product (C) is