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Acyl Halide Reactivity
MCQ questions and answers.
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10
MCQ Questions
1. Which type of compound is commonly used as the acylating agent in Friedel–Crafts acylation?
A.
Acyl chloride
B.
Alkyl alcohol
C.
Alkene
D.
Aromatic amine
Correct Answer:
Acyl chloride
Explanation:
Acyl chlorides are reactive acylating agents that provide the acyl group during Friedel–Crafts acylation.
2. What is the general formula of an acyl chloride used in Friedel–Crafts acylation?
A.
R–OH
B.
R–COCl
C.
R–NH2
D.
R–COOR
Correct Answer:
R–COCl
Explanation:
Acyl chlorides have the general structure R–COCl, containing an acyl group bonded to chlorine.
3. Why are acyl chlorides reactive in Friedel–Crafts acylation?
A.
The carbonyl carbon is electrophilic
B.
The chlorine atom is strongly nucleophilic
C.
They contain an acidic hydroxyl group
D.
They readily form alkenes
Correct Answer:
The carbonyl carbon is electrophilic
Explanation:
The carbonyl carbon in an acyl chloride is electron-deficient, so it can accept electrons from the aromatic ring during acylation.
4. Which Lewis acid is commonly used to activate an acyl chloride in Friedel–Crafts acylation?
A.
AlCl3
B.
NaOH
C.
H2SO4
D.
NH3
Correct Answer:
AlCl3
Explanation:
AlCl3 coordinates with the chlorine atom of the acyl chloride and helps generate the reactive acylium ion.
5. What reactive electrophile is formed from an acyl chloride in the presence of AlCl3?
A.
Acylium ion
B.
Hydroxide ion
C.
Alkoxide ion
D.
Carbanion
Correct Answer:
Acylium ion
Explanation:
Reaction of an acyl chloride with AlCl3 produces an acylium ion, RCO+, which acts as the electrophile.
6. Which bond in an acyl chloride is broken or strongly coordinated during acylium ion formation?
A.
C–Cl bond
B.
C–H bond
C.
C–C bond
D.
O–H bond
Correct Answer:
C–Cl bond
Explanation:
AlCl3 interacts with the chlorine atom, facilitating cleavage of the C–Cl bond and formation of the acylium ion.
7. Which acyl chloride is most directly represented by the formula CH3COCl?
A.
Acetyl chloride
B.
Benzoyl chloride
C.
Propionyl chloride
D.
Formyl chloride
Correct Answer:
Acetyl chloride
Explanation:
CH3COCl is acetyl chloride, a common acyl chloride used to introduce a CH3CO– group in Friedel–Crafts acylation.
8. What acyl group is introduced when benzoyl chloride, C6H5COCl, reacts in Friedel–Crafts acylation?
A.
C6H5CO–
B.
C6H5–
C.
CH3CO–
D.
COCl–
Correct Answer:
C6H5CO–
Explanation:
Benzoyl chloride transfers the benzoyl group, C6H5CO–, to the aromatic ring.
9. Compared with an acyl chloride, which compound is generally less reactive as an acylating agent?
A.
Acid anhydride
B.
Acylium ion
C.
Acetyl chloride
D.
Benzoyl chloride
Correct Answer:
Acid anhydride
Explanation:
Acid anhydrides are generally less reactive than acyl chlorides because the leaving group ability and activation of the acyl group are lower.
10. What is the main role of the chlorine atom in an acyl chloride during Friedel–Crafts acylation?
A.
It acts as a leaving group
B.
It acts as the aromatic ring
C.
It becomes the acyl group
D.
It neutralizes the aromatic compound
Correct Answer:
It acts as a leaving group
Explanation:
Chloride leaves from the acyl chloride after activation by AlCl3, allowing formation of the acylium ion electrophile.
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Acyl Halide Reactivity
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