Alcohol and Phenol

Question 1

What is the bond angle in alcohols compared to the tetrahedral angle?

Answer 1

Slightly greater than the tetrahedral angle

This is due to the repulsive interaction between bulky R groups.

Question 2

What is the C-O bond length in alcohols?

Answer 2

Approximately 41 pm

This bond length is almost the same as in alcohols.

Question 3

How are alcohols prepared from alkenes?

Answer 3

By acid-catalyzed hydration

Alkenes react with water in the presence of an acid catalyst.

Question 4

According to which rule does the addition reaction occur in unsymmetrical alkenes?

Answer 4

Markovnikov’s rule

This rule dictates the regioselectivity of the addition reaction.

Question 5

What is the first step in the mechanism of acid-catalyzed hydration of alkenes?

Answer 5

Protonation of alkene to form carbocation

This occurs via electrophilic attack of H2O.

Question 6

What happens in the second step of the acid-catalyzed hydration mechanism?

Answer 6

Nucleophilic attack of water on carbocation

This step involves the water molecule attacking the positively charged carbocation.

Question 7

What is the final step in the mechanism of acid-catalyzed hydration to form alcohols?

Answer 7

Deprotonation to form an alcohol

This results in the formation of the alcohol from the carbocation.

Question 8

Fill in the blank: Alkenes react with water in the presence of _______ to form alcohols.

Answer 8

acid as catalyst

Question 9

What is hydroboration?

Answer 9

A chemical reaction where borane is added to a double bond, resulting in alcohol formation opposite to Markovnikov’s rule.

Hydroboration typically involves the addition of boron to the carbon atom with more hydrogen atoms.

Question 10

Who reported hydroboration?

Answer 10

HC Brown in 1959.

Brown’s work laid the foundation for understanding hydroboration in organic chemistry.

Question 11

What is the product of hydroboration of an alkene?

Answer 11

An alcohol that appears to have been formed by the addition of water to the alkene.

This reaction is notable for its regioselectivity, contrary to Markovnikov’s rule.

Question 12

What are the starting materials for the reduction of carbonyl compounds to alcohols?

Answer 12

Aldehydes and ketones.

This reduction can be achieved using catalytic hydrogenation or reagents like sodium borohydride (NaBH4) or lithium aluminium hydride (LiAlH4).

Question 13

What type of alcohol is obtained from the reduction of aldehydes?

Answer 13

Primary alcohols.

The reduction process involves the addition of hydrogen in the presence of catalysts.

Question 14

What type of alcohol is obtained from the reduction of ketones?

Answer 14

Secondary alcohols.

Ketones yield secondary alcohols upon reduction.

Question 15

What is the role of lithium aluminium hydride (LiAlH4) in organic synthesis?

Answer 15

It is a strong reducing agent used to reduce carboxylic acids to primary alcohols.

It is also used to convert aldehydes and ketones to their corresponding alcohols.

Question 16

What is the process to reduce carboxylic acids to alcohols commercially?

Answer 16

Convert them to esters followed by reduction using hydrogen in the presence of a catalyst.

This method is preferred due to the high cost of lithium aluminium hydride.

Question 17

What catalysts are typically used for the reduction of carbonyl compounds?

Answer 17

Finely divided metals such as platinum, palladium, or nickel.

These catalysts facilitate the addition of hydrogen to carbonyl groups.

Question 18

Fill in the blank: Aldehydes yield _______ upon reduction.

Answer 18

primary alcohols

Question 19

Fill in the blank: Ketones yield _______ upon reduction.

Answer 19

secondary alcohols

Question 20

True or False: The addition of borane to a double bond follows Markovnikov’s rule.

Answer 20

False

Hydroboration results in a product that is contrary to Markovnikov’s rule.

Question 21

Commercial prep of alcohol from carboxylic acid reaction

Answer 21

RCOOH in presence of R’OH AND H+ gives RCOOR’ which on rexn with h2 and catalyst give RCH2OH + R’OH

Question 22

What type of alcohol is produced when Grignard reagents react with methanal?

Answer 22

Primary alcohol

Methanal is the simplest aldehyde, leading to the formation of a primary alcohol.

Question 23

What type of alcohol is produced when Grignard reagents react with other aldehydes?

Answer 23

Secondary alcohol

Other aldehydes lead to the formation of secondary alcohols through Grignard reactions.

Question 24

What type of alcohol is produced when Grignard reagents react with ketones?

Answer 24

Tertiary alcohol

Ketones react with Grignard reagents to yield tertiary alcohols.

Question 25

What is the first step in the reaction of Grignard reagents with carbonyl compounds?

Answer 25

Nucleophilic addition to the carbonyl group ## Footnote This step forms an adduct before further reactions occur.

Question 26

What happens to the adduct formed in the reaction of Grignard reagents with carbonyl compounds?

Answer 26

Hydrolysis yields an alcohol ## Footnote The adduct undergoes hydrolysis to produce the final alcohol product.

Question 27

Complete the reaction: RCHO + RMgX → _______.

Answer 27

RCH(OH)MgX ## Footnote This reaction illustrates the formation of an alcohol from an aldehyde and a Grignard reagent.

Question 28

Complete the reaction: RCOR + R'MgX → _______.

Answer 28

R-C(OH)R' + Mg(OH)X ## Footnote This reaction shows the production of a tertiary alcohol from a ketone.

Question 29

What is the general role of Grignard reagents in organic synthesis?

Answer 29

To produce alcohols from carbonyl compounds ## Footnote Grignard reagents are powerful nucleophiles used to form alcohols by reacting with aldehydes and ketones.

Question 30

True or False: Grignard reagents can react with both aldehydes and ketones.

Answer 30

True ## Footnote Grignard reagents are versatile and can react with various carbonyl compounds.

Question 31

What is the primary source of worldwide phenol production?

Answer 31

Cumene ## Footnote Cumene (isopropylbenzene) is the main hydrocarbon used for phenol production.

Question 32

What is the process to obtain phenol from chlorobenzene?

Answer 32

Fused with NaOH at 623K and 320 atmosphere pressure ## Footnote This process involves the acidification of the produced haloarenes.

Question 33

How is phenol produced from benzenesulphonic acid?

Answer 33

Benzene is sulphonated with oleum and then converted to sodium phenoxide ## Footnote The sodium phenoxide is then acidified to yield phenol.

Question 34

What is the role of sodium hydroxide in phenol production from sulphonated benzene?

Answer 34

Converts benzene sulphonate to sodium phenoxide ## Footnote This reaction is part of the overall process to obtain phenol.

Question 35

What is the process to obtain phenol from diazonium salts?

Answer 35

Diazonium salts are hydrolysed by warming with water or treating with dilute acids ## Footnote A diazonium salt is formed by treating an aromatic primary amine with nitrous acid.

Question 36

What temperature range is used for forming diazonium salts?

Answer 36

273-278 K ## Footnote This temperature is critical for the stability of diazonium salts.

Question 37

What is the method to produce phenol from cumene?

Answer 37

Oxidation of cumene to cumene hydroperoxide, then treated with dilute acid ## Footnote This reaction also produces acetone as a by-product.

Question 38

What by-product is formed during the production of phenol from cumene?

Answer 38

Acetone ## Footnote Acetone is produced alongside phenol during its synthesis from cumene.

Question 39

Fill in the blank: Phenol is obtained from __________ by acidification.

Answer 39

Sodium phenoxide ## Footnote Sodium phenoxide is an intermediate in the production of phenol.

Question 40

True or False: Phenol can be produced by hydrolysing diazonium salts.

Answer 40

True ## Footnote Hydrolysis of diazonium salts is a recognized method for phenol synthesis.

Question 41

What is formed when cumene hydroperoxide is treated with dilute acid?

Answer 41

Phenol and acetone ## Footnote This reaction is a significant industrial process for producing phenol.