HYDROCARBON

Question 1

What type of reaction is the Wurtz reaction?

Answer 1

The Wurtz reaction is a coupling reaction.

Question 2

What are the starting materials in a Wurtz reaction?

Answer 2

The starting materials in a Wurtz reaction are alkyl halides.

Question 3

What is the role of sodium or lithium in a Wurtz reaction?

Answer 3

Sodium or lithium act as reducing agents in a Wurtz reaction.

Question 4

What is the main product of a Wurtz reaction?

Answer 4

The main product of a Wurtz reaction is an alkane.

Question 5

What is the mechanism of a Wurtz reaction?

Answer 5

The mechanism of a Wurtz reaction involves the generation of free radicals from alkyl halides, which then combine to form a new bond.

Question 6

Order of Reactivity Of Alkyl Halide in Wurtz Rxn ?

Answer 6

R-I>R-Br>R-Cl

Question 7

What is the general formula of a Gilman reagent?

Answer 7

The general formula of a Gilman reagent is R2CuLi , where R represents alkyl or aryl groups.

Question 8

What is the chemical name of Gillman reagent ?

Answer 8

Dialkyl Lithium Cuprate

Question 9

What is the first step in the preparation of a Gilman reagent ?

Answer 9

In the first step, an alkyl halide (R-X) reacts with lithium metal (Li) in dry ether to form an organolithium compound (R-Li).

Question 10

What happens in the second step of the Gilman reagent preparation?

Answer 10

In the second step, the organolithium compound (R-Li) reacts with copper(I) iodide (CuI) to form the Gilman reagent .

Question 11

What is the key reaction Gilman reagents undergo to form alkanes?

Answer 11

Gilman reagents undergo SN2 reactions with alkyl halides (R-X), where the alkyl group from the Gilman reagent replaces the halide, forming an alkane.

Question 12

Which types of alkyl halides are most commonly used in the preparation of alkanes from Gilman reagents ?

Answer 12

Primary alkyl halides are most commonly used due to their higher reactivity in SN2 reactions compared to secondary or tertiary alkyl halides.

Tertiary alkyl halides do not undergo this reaction because these are least reactive towards SN2 reaction

Question 13

What is the byproduct formed along with the alkane during the reaction between a Gilman reagent and an alkyl halide?

Answer 13

The byproducts are R-Cu (an organocopper compound) and LiX (lithium halide).

Question 14

What role does the Gilman reagent play in the reaction to form an alkane?

Answer 14

The Gilman reagent, acts as a nucleophile, where one of the groups attacks the electrophilic carbon of the alkyl halide (R’-X), displacing the halide and forming an alkane.

Question 15

What is Kolbe electrolysis?

Answer 15

Kolbe electrolysis is an electrochemical process in which carboxylate salts undergo decarboxylation at the anode to produce alkanes. This process requires flow of electricity.

Question 16

What type of carboxylates are typically used in Kolbe electrolysis?

Answer 16

Sodium or potassium salts of carboxylic acids (RCOONa or RCOOK)

Question 17

What happens at the anode during Kolbe electrolysis?

Answer 17

At the anode, carboxylate ions are oxidized, releasing carbon dioxide (CO2) and generating a free alkyl radical (R·), which dimerizes to form an alkane (R-R).

Question 18

What are some limitations of Kolbe electrolysis?

Answer 18

Do not produce alkane if alkyl group of carboxylate is 3° (Here ESTER is produced)

Question 19

What is a Grignard reagent?

Answer 19

A Grignard reagent is an organomagnesium compound, represented as R-MgX, where R is an alkyl or aryl group and X is a halogen.

Question 20

How are Grignard reagents typically prepared?

Answer 20

Grignard reagents are prepared by reacting an alkyl or aryl halide (R-X) with magnesium metal (Mg) in an anhydrous ether solvent.

Question 21

What is the general reaction for forming an alkane from a Grignard reagent?

Answer 21

Grignard reagents react with water or protic solvents to form alkanes and magnesium hydroxide salts.

R-MgX + H2O —-> R-H + Mg(OH)X

Question 22

What are the reagents used in Wolff-Kishner reduction & Clemmensen reduction?

Answer 22

Wolff-Kishner Reduction: Hydrazine (N₂H₄), Strong Base (KOH or NaOH), heat

Clemmensen Reduction: Zinc amalgam (Zn-Hg), HCl

Question 23

Which compounds can be reduced using Wolff-Kishner and Clemmensen reductions, and what are the resulting products?

Answer 23

=>Wolff-Kishner Reduction: Reduces aldehydes and ketones to alkanes.

=>Clemmensen Reduction: Reduces aldehydes and ketones to alkanes.

Question 24

Which compounds can be reduced using Red P + HI, and what are the resulting products?

Answer 24

Red phosphorus (Red P) and hydroiodic acid (HI) act as a powerful reducing agent, commonly used to reduce oxygen-containing functional groups like alcohols, carbonyls to Alkanes

Question 25

How does LiAlH₄ reduce alcohols, carboxylic acids, esters, ketones, aldehydes, nitriles, and amides, and what are the resulting products?

Answer 25

1. Alcohol: No reaction.
2. Carboxylic acid (R-COOH): Reduced to primary alcohol (R-CH₂OH).
3. Ester (R-COOR’): Reduced to primary alcohol (R-CH₂OH + R’OH).
4. Ketone (R-CO-R’): Reduced to secondary alcohol (R-CHOH-R’).
5. Aldehyde (R-CHO): Reduced to primary alcohol (R-CH₂OH).
6. Nitrile (R-CN): Reduced to primary amine (R-CH₂NH₂).
7. Amide (R-CONH₂): Reduced to amine (R-CH₂NH₂).