Free Alkyl Halides MCQs with Answers
458 Alkyl Halides MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Alkyl halides are named and related to their carbon-halogen structure, polarity and reactivity. The key reactions are nucleophilic substitution by SN1 and SN2 mechanisms and elimination by E1 and E2 mechanisms, including how substrate structure, nucleophile, base, solvent and temperature influence substitution versus elimination.
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Read the Alkyl Halides notesFree MDCAT chapter notes with key terms458 questions · page 2 of 23
- A. Addition
- B. Elimination
- C. Base
- D. Heat
Explanation: A vicinal dihalide is converted to an alkyne by removing two molecules of hydrogen halide with hot alcoholic potassium hydroxide, which is…
Correct answer: Addition- A. 1-bromopentane
- B. 1-bromo-2,2,2-trimethylethane
- C. 1-bromo-2,2-dimethylpropane
- D. 2-bromopentane
Explanation: The longest chain containing the bromine has three carbons, giving propane, with the bromine on carbon 1 and two methyl groups on carbon…
Correct answer: 1-bromo-2,2-dimethylpropane- A. first order kinetics
- B. second order kinetics
- C. third order kinetics
- D. zero order kinetics
Explanation: An E2 elimination occurs in one concerted step and its rate depends on both the substrate and the base, so the rate law contains two…
Correct answer: second order kinetics- A. the concentration of substrate
- B. the concentration of nucleophile
- C. the concentration of substrate as well as nucleophile
- D. base the concentration of substrate as well as nucleophile
Explanation: In an E1 reaction, the slow rate-determining step is ionisation of the substrate to form a carbocation, so rate = k[substrate].
Correct answer: the concentration of substrate- A. halogenation
- B. dehalogenation
- C. dehydrohalogenation
- D. hydrohalogenation
Explanation: Removal of a hydrogen atom and a halogen atom from adjacent carbon atoms is dehydrohalogenation, usually producing an alkene.
Correct answer: dehydrohalogenation26. The best method of preparation of alkyl halides is a reaction of alcohol with__________________?
- A. Zn / HCI
- B. SOCl2 / Pyridine
- C. PCI3
- D. PCI5
Explanation: Thionyl chloride in pyridine is an efficient reagent for converting alcohols into alkyl chlorides, producing gaseous by-products such as…
Correct answer: SOCl2 / Pyridine- A. two
- B. three
- C. one
- D. four
Explanation: In a primary alkyl halide, the carbon attached to the halogen is bonded to only one other carbon atom, as in CH3CH2Cl.
Correct answer: one- A. C-F
- B. C-C
- C. C-Br
- D. C-I
Explanation: Among the listed bonds, C-F has the greatest bond energy because fluorine forms a short, strong bond with carbon due to its small atomic…
Correct answer: C-F- A. Flouride ion
- B. Bromide ion
- C. Chloride ion
- D. Iodide ion
Explanation: In a polar aprotic solvent, fluoride ion is strongly nucleophilic because it is not extensively hydrogen-bonded or solvated by the…
Correct answer: Flouride ion- A. Inversion
- B. Retention
- C. Recemic Mixture
- D. Stereospecific
Explanation: An SN1 reaction forms a planar carbocation intermediate, so the nucleophile can attack from either side and usually gives a racemic…
Correct answer: Recemic Mixture- A. Glycols
- B. Vicinal dihalides
- C. Geminal dihalides
- D. Diols
Explanation: A compound with two halogen atoms attached to adjacent carbon atoms contains a vicinal dihalide, with the substituents on neighbouring…
Correct answer: Vicinal dihalides- A. Water
- B. Hexane
- C. Dimethylflormamide
- D. Ethanol
Explanation: SN2 reactions are fastest in polar aprotic solvents because these solvents dissolve ions without strongly solvating and slowing the…
Correct answer: Dimethylflormamide- A. CH3Br
- B. CH3CH2Br
- C. CH3CH2CH2Br
- D. (CH3)3CBr
Explanation: SN1 reactions proceed through a carbocation, so the substrate that forms the most stable carbocation reacts most readily.
Correct answer: (CH3)3CBr- A. Nucleophilic substitution
- B. Nucleophilic addition
- C. Elimination
- D. both A & C
Explanation: The carbon-halogen bond in an alkyl halide can undergo nucleophilic substitution, while a base can remove a hydrogen and cause…
Correct answer: both A & C- A. they have an electrophilic carbon
- B. they have an electrophilic carbon & a good leaving group
- C. they have an electrophilic carbon & a bad leaving group
- D. they have a nucleophilic carbon & a good leaving group
Explanation: The carbon bonded to halogen is electron-deficient because the halogen withdraws electron density, making that carbon electrophilic.
Correct answer: they have an electrophilic carbon & a good leaving group- A. E1 + E2
- B. E2 + SN2
- C. E1 and SN1
- D. SN1 and SN2
Explanation: E1 and SN1 reactions both begin with ionization of the carbon-halogen bond to form a carbocation, which is the slow, rate-determining…
Correct answer: E1 and SN1- A. primary alkyl halide
- B. secondary alkyl halide
- C. tertiary alkyl halide
- D. all
Explanation: SN2 reactions require backside attack by the nucleophile, so steric hindrance must be small; primary alkyl halides provide the least…
Correct answer: primary alkyl halide- A. CH3-X
- B. (CH3)3 C-CH2 - X
- C. (CH3)2 CH - X
- D. (CH3)3 C - X
Explanation: A secondary alkyl halide has enough substitution to form a carbocation under SN1 conditions but is not so crowded that SN2 attack is…
Correct answer: (CH3)2 CH - X- A. C2H5O-
- B. SCN-
- C. NH3
- D. H3C+
Explanation: A nucleophile donates an electron pair, so C2H5O-, SCN- and NH3 can attack an electron-deficient centre.
Correct answer: H3C+- A. R-F
- B. R-C
- C. R-Br
- D. R-I
Explanation: For the same alkyl group, leaving-group ability increases from fluoride to iodide because the C-I bond is weaker and I- is more stable and…
Correct answer: R-I