250+ TOP MCQs on Meso Structures and Answers

Organic Chemistry Multiple Choice Questions on “Meso Structures”.

1. Which of the following is the definition of a meso compound?
a) A molecule with chirality centers which is chiral
b) A chiral compound with more than one chirality center
c) A diastereomer with no chirality centers
d) A molecule with chirality centers which is not chiral
Answer: d
Clarification: Meso compounds are not chiral. Molecule with chirality centers which is chiral are false. So, other statements are false.

2. A compound whose molecules are superimposable on their mirror images even though they contain asymmetric carbon atoms is called
a) A threo compound
b) A meso compound
c) A unsymmetric compound
d) An erythro compound
Answer: b
Clarification: Meso compounds are possible if two (or more) chirality centers in a molecule have the same set of four substituents. Examination of molecular models might help you when examining stereoisomers.

3. Which of the following compounds is a meso compound?
a) (2R,3R)-dibromobutane
b) (2R,3S)-dibromobutane
c) (2R,3S)-3-bromo-2-butanol
d) (2R,3R)-3-bromo-2-butanol
Answer: b
Clarification: (2R,3S)-Dibromobutane is superimposable on its mirror image, so it is achiral (i.e., not chiral). Achiral molecules which have chirality centers are called meso compounds. Meso compounds are possible if two (or more) chirality centers in a molecule have the same set of four substituents. Examination of molecular models might help you when examining stereoisomers.

4. Which statement is not true for a meso compound?
a) The specific rotation is 0°
b) There are one or more planes of symmetry
c) A single molecule is identical to its mirror image
d) The stereochemical labels, (R) and (S), must be identical for each stereogenic center
Answer: d
Clarification: Statement stereochemical labels, (R) and (S), must be identical for each stereogenic center is not true about meso compounds, stereochemical labels, (R) and (S), can or cannot be identical for each stereogenic center.

5. Which is a meso compound?
a) (2R,3R)-2,3-Dibromobutane
b) (2R,3S)-2,3-Dibromopentane
c) (2R,4R)-2,4-Dibromopentane
d) (2R,4S)-2,4-Dibromopentane
Answer: d
Clarification: (2R,4S)-Dibromopentane is superimposable on its mirror image, so it is achiral (i.e., not chiral). Achiral molecules which have chirality centers are called meso compounds. Meso compounds are possible if two (or more) chirality centers in a molecule have the same set of four substituents. Examination of molecular models might help you when examining stereoisomers.

6. Which of the following is a mesocompound?

a) I
b) II
c) III
d) IV
Answer: a
Clarification: Compound I is superimposable on its mirror image, so it is achiral. Achiral molecules which have chirality centers are called meso compounds. Meso compounds are possible if two (or more) chirality centers in a molecule have the same set of four substituents. Examination of molecular models might help you when examining stereoisomers.

7. The given compound is meso compound.

a) True
b) False
Answer: a
Clarification: The given compound is superimposable on its mirror image, so it is achiral. Achiral molecules which have chirality centers are called meso compounds. Meso compounds are possible if two (or more) chirality centers in a molecule have the same set of four substituents. Examination of molecular models might help you when examining stereoisomers.

8. Which of the following is(are) not meso compound(s)?

a) II
b) II and III
c) I and III
d) I and II
Answer: a
Clarification: Meso compounds are possible if two (or more) chirality centers in a molecule have the same set of four substituents. Examination of molecular models might help you when examining stereoisomers.

9. Which of the following is(are) not meso compound(s)?

a) I
b) II and III
c) I and III
d) I and II
Answer: b
Clarification: Meso compounds are possible if two (or more) chirality centers in a molecule have the same set of four substituents. Examination of molecular models might help you when examining stereoisomers.

10. Which is the meso isomer of butane-1,2,3,4-tetraol?
a)
b)
c)
d)
Answer: b
Clarification: If we redraw each structure with the OH groups (for example) on C2 and C3 eclipsed, or re-write the structures as Fischer projections, then we can see more easily which structure has a mirror plane between C2 and C3. And this condition will satisfy the meso compound.