Alkyl halides are commonly known as haloalkanes. They are open-chain hydrocarbons in which the hydrogen atom is replaced with the halogen atom. We can classify alkyl halides into different classes based on how the halogen atom is positioned in the open-chain hydrocarbon.
| Definition: Alkyl halides are open-chain hydrocarbons in which the hydrogen atom is replaced with the halogen atom. |
Alkyl Halide Chemistry Questions with Solutions
Q1. What is the order of SN2 reaction of the alkyl halide?
(a) RCl > RBr > RF > RI
(b) RI > RBr > RCl > RF
(c) R-F > R-Cl > RBr > RI
(d) RBr > RI > RCl > RF
Answer: (b) The order of SN2 reaction of the alkyl halide is RI > RBr > RCl > RF.
Explanation: Iodine is a good nucleophile and a good leaving group. Thus, it eliminates easily from an alkyl halide favouring SN2 elimination reaction.
Q2. Chloroform is used as an
(a) Antiseptic
(b) Anaesthetic
(c) Antipyretic
(d) None of the above
Answer: (b) Chloroform is used as an anaesthetic.
Q3. Methyl chloride reacts with silver acetate to yield
(a) Acetic acid
(b) Methyl acetate
(c) Acetyl chloride
(d) None of the above
Answer: (b) Methyl chloride reacts with silver acetate to yield methyl acetate.
Q4. The given reaction is an example of?
C2H5Br + KCN (aq) β C2H5CN + KBr
(a) Elimination reaction
(b) Nucleophilic substitution reaction
(c) Electrophilic substitution reaction
(d) None of the above
Answer: (c) The given reaction: C2H5Br + KCN (aq) β C2H5CN + KBr is an example of electrophilic substitution reaction.
Q5. An alkyl halide can be converted into alcohol by the
(a) Addition reaction
(b) Substitution reaction
(c) Dehydrohalogenation reaction
(d) None of the above
Answer: (b) An alkyl halide can be converted into alcohol by the substitution reaction.
Q6. Write the IUPAC name of (CH3)3 C CH2Br.
Answer: The IUPAC name of (CH3)3 C CH2Br is 1-Bromo-2, 2-dimethyl propane.
1-Bromo-2, 2-dimethyl propane
Q7. Why do we keep chloroform in the dark coloured bottles?
Answer: We keep chloroform in the dark coloured bottles because it reacts with atmospheric oxygen to produce poisonous phosgene gas.
Q8. Conver Prop-1-ene to 1-fluoro propane.
Answer: We can convert Prop-1-ene to 1-fluoro propane by reacting Prop-1-ene with hydrogen bromide in the presence of hydrogen peroxide, followed by the reaction with AgF.
Q9. What happens when n-butyl chloride reacts with alcoholic KOH?
Answer: An elimination reaction takes place when n-butyl chloride reacts with alcoholic KOH to form an unsaturated But-1-ene.
Q10. Draw the structure of 1-Bromo-4-chloro but-2-ene
Answer: The structure of 1-Bromo-4-chloro but-2-ene is mentioned below.
Q11. Distinguish between an alkyl halide and an aryl halide.
Answer:
| S. No. | Alkyl Halide | Aryl Halide |
| 1. | Alkyl halides are open-chain hydrocarbons in which the hydrogen atom is replaced with the halogen atom. | Aryl halides are aromatic hydrocarbons in which the hydrogen atom is replaced with the halogen atom. |
| 2. | The halogen atom is attached to the sp3 hybridised carbon atom. | The halogen atom is attached to an sp2 hybridised carbon atom. |
| 3. | They are linear or branched. | They are ringed. |
| 4. | They undergo nucleophilic substitution reactions. | They do not undergo nucleophilic substitution reactions. |
Q12. Match the following.
| Column I | Column II |
| Vinyl halide | CH3 CH = CH CH2 Cl |
| Alkyl halide | C6H5(CH2Cl) |
| Allyl halide | CH2 = CHX |
| Benzyl halide | CH3 – CH2 X |
Answer:
| Column I | Column II |
| Vinyl halide | CH2 = CHX |
| Alkyl halide | CH3 – CH2 X |
| Allyl halide | CH3 CH = CH CH2 Cl |
| Benzyl halide | C6H5(CH2Cl) |
Q13. Why is alkyl halide insoluble in water?
Answer: An alkyl halide is insoluble in water because it can not form a hydrogen bond with water. Thus, it is insoluble in water.
Q14. What is sandmeyer’s reaction?
Answer: The Sandmeyer reaction is an organic reaction used to synthesise aryl halides from aryl diazonium salts using copper chlorides as a reagent.
Q15. Convert 2-Bromo butane to but-2-ene.
Answer: We can convert 2-Bromo butane to but-2-ene by reacting it with alcoholic KOH. When alcoholic KOH reacts with 2-Bromo butane an elimination reaction takes place, leading to the elimination of HBr and the required but-2-ene is formed.
Practise Questions on Alkyl Halide
Q1. Arrange the following compounds in the increasing order of reactivity towards an SN2 reaction.
2-Bromo-2- methyl butane, 1-Bromo pentane, 2-Bromo pentane
Q2. Convert aniline to chlorobenzene.
Q3. Why is allyl chloride hydrolysed more readily than n-propyl chloride?
Q4. What is Ξ² elimination of alkyl halide?
Q5. Explain the optical activity of 2-Chlorobutane.
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