HALOALKANE 2

Question 1

What happens to the hydroxyl group of an alcohol when it reacts with concentrated halogen acids,Phosphorous halide, Thionyl Chloride

Answer 1

Hyrdoxyl group is replaced by halogen

Question 2

Why is thionyl chloride (SOCl₂) preferred for converting alcohols to alkyl halides?

Answer 2

Thionyl chloride is preferred because it forms alkyl halides along with gaseous byproducts (SO₂ and HCl)

Question 3

What catalyst is required for the reaction of primary and secondary alcohols with HCl to form alkyl halides?

Answer 3

Zinc chloride (ZnCl₂) is required as a catalyst.

Question 4

How is the reaction of tertiary alcohols with concentrated HCl conducted?

Answer 4

The reaction is conducted by simply shaking the tertiary alcohol with concentrated HCl at room temperature.

Question 5

What method is used to prepare alkyl bromides from alcohols?

Answer 5

Constant boiling with 48% HBr is used to prepare alkyl bromides.

Question 6

How can good yields of alkyl iodides (R—I) be obtained from alcohols?

Answer 6

By heating alcohols with sodium or potassium iodide in 95% orthophosphoric acid.

Question 7

What is the order of reactivity of alcohols with a given haloacid?

Answer 7

The order of reactivity is tertiary (3°) > secondary (2°) > primary (1°).

Question 8

How are phosphorus tribromide (PBr₃) and triiodide (PI₃) typically generated for alcohol reactions?

Answer 8

They are generated in situ by reacting red phosphorus with bromine and iodine

Question 9

How is alkyl chloride prepared using dry hydrogen chloride gas?

Answer 9

By passing dry hydrogen chloride gas through a solution of alcohol.

Question 10

What is another method to prepare alkyl chloride?

Answer 10

By heating a mixture of alcohol and concentrated aqueous halogen acid.

Question 11

Why are these methods not suitable for preparing aryl halides?

Answer 11

Because the carbon-oxygen bond in phenols has partial double bond character

Question 12

What are the products of the reaction R-OH + HCl (with ZnCl₂ catalyst)?

Answer 12

R-Cl + H₂O

Question 13

What are the products of the reaction R-OH + NaBr + H₂SO₄?

Answer 13

R-Br + NaHSO₄ + H₂O

Question 14

What are the products of the reaction 3R-OH + PX₃ (X = Cl

Answer 14

Br2

Question 15

What are the products of the reaction R-OH + PCl₅?

Answer 15

R-Cl + POCl₃ + HCl

Question 16

What are the products of the reaction R-OH + red P/X₂ (X₂ = Br₂

Answer 16

I₂

Question 17

What are the products of the reaction R-OH + SOCl₂?

Answer 17

R-Cl + SO₂ + HCl

Question 18

What type of reaction occurs when an alkene reacts with hydrogen halides?

Answer 18

Addition reaction

Question 19

Which hydrogen halides can react with alkenes to form alkyl halides?

Answer 19

Hydrogen chloride (HCl)

Question 20

What is the major product formed when propene reacts with a hydrogen halide?

Answer 20

The product that follows Markovnikov’s rule

Question 21

What is Markovnikov’s rule?

Answer 21

In the addition of hydrogen halides to alkenes

Question 22

Why does propene yield two products when reacting with a hydrogen halide?

Answer 22

Because the addition of the hydrogen halide can occur in two possible ways

Question 23

What is the purpose of adding bromine in CCl4 to an alkene in the laboratory?

Answer 23

To detect the presence of a double bond in a molecule

Question 24

What is observed when bromine in CCl4 is added to an alkene?

Answer 24

The reddish-brown color of bromine is discharged

Question 25

What type of compound is synthesized when bromine is added to an alkene?

Answer 25

Vic-dibromides (colorless compounds).

Question 26

What are vic-dibromides?

Answer 26

Compounds formed by the addition of bromine to an alkene

Question 27

What is the outcome of free radical chlorination or bromination of alkanes?

Answer 27

A complex mixture of isomeric mono- and polyhaloalkanes is produced.

Question 28

Why is the mixture obtained from free radical chlorination or bromination of alkanes difficult to separate?

Answer 28

Because it contains a complex mixture of isomeric mono- and polyhaloalkanes

Question 29

What is the yield of any single compound in free radical chlorination or bromination of alkanes?

Answer 29

The yield of any single compound is low due to the formation of a complex mixture of isomers.

Question 30

What types of compounds are formed in free radical chlorination or bromination of alkanes?

Answer 30

Isomeric mono- and polyhaloalkanes.

Question 31

What is the Finkelstein reaction?

Answer 31

A reaction where alkyl chlorides or bromides react with NaI in dry acetone to form alkyl iodides

Question 32

What are the reactants in the Finkelstein reaction?

Answer 32

Alkyl chlorides or bromides (R-X) and sodium iodide (NaI) in dry acetone.

Question 33

What are the products of the Finkelstein reaction?

Answer 33

Alkyl iodides (R-I) and sodium chloride or sodium bromide (NaX)

Question 34

Why does the Finkelstein reaction proceed forward according to Le Chatelier’s Principle?

Answer 34

Because the precipitation of NaCl or NaBr removes the product from the solution

Question 35

What role does dry acetone play in the Finkelstein reaction?

Answer 35

It facilitates the reaction by allowing the precipitation of NaCl or NaBr

Question 36

What is the Swarts reaction?

Answer 36

A reaction where alkyl chlorides or bromides are heated with a metallic fluoride (such as AgF

Question 37

What are the reactants in the Swarts reaction?

Answer 37

Alkyl chlorides or bromides and a metallic fluoride (e.g.

Question 38

What is the product of the Swarts reaction?

Answer 38

Alkyl fluorides.

Question 39

Why is the Swarts reaction used for synthesizing alkyl fluorides?

Answer 39

It is an effective method to replace chlorine or bromine in alkyl halides with fluorine using metallic fluorides.

Question 40

What are the reactants in the reaction: H3C-Br + AgF?

Answer 40

H3C-Br and AgF.

Question 41

What are the products in the reaction: H3C-Br + AgF?

Answer 41

H3C-F and AgBr.

Question 42

What is the purpose of adding bromine in CCl4 to an alkene in the laboratory?

Answer 42

To detect the presence of a double bond in a molecule

Question 43

What is observed when bromine in CCl4 is added to an alkene?

Answer 43

The reddish-brown color of bromine is discharged

Question 44

What type of compound is synthesized when bromine is added to an alkene?

Answer 44

Vic-dibromides (colorless compounds).

Question 45

What are vic-dibromides?

Answer 45

Compounds formed by the addition of bromine to an alkene

Question 46

How can aryl chlorides and bromides be prepared?

Answer 46

They can be prepared by electrophilic substitution of arenes with chlorine and bromine

Question 47

Why can ortho and para isomers be easily separated?

Answer 47

Due to the large difference in their melting points.

Question 48

Why are reactions with iodine reversible

Answer 48

and what is required to drive iodination?

Question 49

Why are fluoro compounds not prepared by electrophilic substitution?

Answer 49

Due to the high reactivity of fluorine.

Question 50

What are the reactants in the halogenation of toluene in the presence of Fe?

Answer 50

Toluene (CH₃) and a halogen (X₂

Question 51

What are the products of the halogenation of toluene in the presence of Fe?

Answer 51

o-Halotoluene and p-Halotoluene (ortho and para isomers of halotoluene).

Question 52

What is the starting material in Sandmeyer’s reaction?

Answer 52

A primary aromatic amine.

Question 53

What is the first step in Sandmeyer’s reaction?

Answer 53

The primary aromatic amine is dissolved or suspended in cold aqueous mineral acid and treated with sodium nitrite to form a diazonium salt.

Question 54

What happens after the diazonium salt is formed in Sandmeyer’s reaction?

Answer 54

The freshly prepared diazonium salt solution is mixed with cuprous chloride (CuCl) or cuprous bromide (CuBr).

Question 55

What is the final product of Sandmeyer’s reaction?

Answer 55

The diazonium group is replaced by –Cl or –Br

Question 56

How is the diazonium group replaced by iodine in the preparation of aryl iodides?

Answer 56

The diazonium salt is shaken with potassium iodide (KI)

Question 57

What is required to replace the diazonium group with chlorine or bromine in Sandmeyer’s reaction?

Answer 57

Cuprous chloride (CuCl) or cuprous bromide (CuBr).

Question 58

What is unique about the replacement of the diazonium group by iodine compared to chlorine or bromine?

Answer 58

It does not require cuprous halide; instead

Question 59

What is the role of potassium iodide in the preparation of aryl iodides?

Answer 59

It provides the iodide ion (I⁻) that replaces the diazonium group.

Question 60

Why is cuprous halide not needed for the replacement of the diazonium group by iodine?

Answer 60

The reaction proceeds readily by direct interaction of the diazonium salt with potassium iodide.