Test: Stereochemistry Level - 1


20 Questions MCQ Test Organic Chemistry | Test: Stereochemistry Level - 1


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Attempt Test: Stereochemistry Level - 1 | 20 questions in 20 minutes | Mock test for Chemistry preparation | Free important questions MCQ to study Organic Chemistry for Chemistry Exam | Download free PDF with solutions
QUESTION: 1

Which one of the following statement is true?

Solution:

Diastereomers have different physical properties. They can be separated by ordinary separation techniques such as fractional crystallization.

QUESTION: 2

On Pluto, where everything is frozen, astronauts discovered two forms of 1, 2-dibromoethane; gauche and anti. Assuming that there are no rotations around single bonds, which statement about the two forms is correct:

Solution:

Gauche and anti-conformers are stereoisomers not related by mirror-image relationship, hence diastereomers.

QUESTION: 3

Which type of conformation is shown by I and II?

Solution:
QUESTION: 4

The most stable conformation of ethylene glycol is ______.

Solution:
  • Fully eclipsed conformation: the rotation of the gauge conformation to 60 degrees results in the gauge conformation and it is the least stable conformation of all.
  • Hence, the most stable conformation of ethylene glycol is gauche conformation.
QUESTION: 5

In the boat conformation of cyclohexane, the most destabilizing interaction is:

Solution:
  • Eclipsed atoms are not valid in boat configurations.

  • Flagpole interaction generally raises the strain and then energy in cyclohexane (boat conformational structure).
  • You can imagine this as two hydrogen atoms at pole position (1, 4) and the interaction between them.
  • The boat conformations have higher energy than the chair conformations. The interaction between the two flagpole hydrogen atoms, in particular, generates steric strain.
  • Torsional strain also exists between the C2–C3 and C5–C6 bonds, which are eclipsed. Because of this strain, the boat configuration is unstable (i.e. is not a local energy minimum).

Hence D is correct.

QUESTION: 6

The reaction in which stereochemically different molecules react differently is called:

Solution:
  • The reaction in which stereochemically different molecules react differently is called stereospecific reaction.
  • Stereospecificity is the property of a reaction mechanism that lead to different stereoisomeric reaction products from different stereoisomeric reactants, or which operates on only one of the stereoisomers.
QUESTION: 7

The configurations at the two stereocentres in the compound given below are:

Solution:
QUESTION: 8

The configuration at the two stereocentres in the compound given below are:

Solution:
QUESTION: 9

The two compounds given below are:

Solution:
QUESTION: 10

In the following Markonikov addition reaction, the products A and B are:

Solution:
QUESTION: 11

Epoxidation of (R)-cyclohexene-2-ol with peracetic acid yields a 95:5 mixture of compounds A and B compounds A and B are:

Solution:
QUESTION: 12

Among the following the most stable isomer for 3-methoxycylohexanol is:

Solution:
  • There is a possibility of Hydrogen Bonding between "Hydrogen(H)" of OH group and "Oxygen(O)" of OMe group. 
  • So if they are oriented in such a way that these two groups are close to each other , the strength of hydrogen bond would increase making it more stronger.
  • Hence, Option A, because of Hydrogen Bonding becomes the most stable isomer. 
QUESTION: 13

What is the relation between shown compounds?

Solution:
QUESTION: 14

Which of the following term best describes the pair of compounds shown?

Solution:
QUESTION: 15

The first person to separate a racemic mixture into individual enantiomers is:

Solution:

Louis Pasteur was the first documented person to separate stereoisomers.

QUESTION: 16

Among the following dibromocyclohexanes, the one that reacts fastest with sodium iodide to give cyclohexene is:

Solution:
  • The above reaction is an example of E2 elimination.
  • For E2 elimination both the leaving group must be anti w.r.t each other in the adjacent carbon atoms.
  • In option C, we get this requirement of anti geometry of the Br atoms, so it undergoes reaction. 
     
QUESTION: 17

What is the stereochemical relationship between the following two molecules?

organic-chemistry-questions-answers-stereochemistry-q6

Solution:

Both molecules have the same molecular formula (C9H16BrCl) and the same connectivity. Each molecule also has three stereocenters, marked above with an asterisk, and does not contain a plane of symmetry. Therefore, both molecules are chiral. Using one of the methods outlined in this tutorial, it can be determined that these molecules are superimposable. Therefore, the molecules are identical.

QUESTION: 18

Which structure is different from the following?

Solution:

The two substituents in the cis 1,4-disubstituted chair cyclohexane shown are necessarily axial and equatorial, as in (a), (b) and (d). In (c), however, the 1,4-substituents are both equatorial so this is the trans isomer, i.e. a different compound.

QUESTION: 19

The correct order of stability for the following conformations of cyclohexane is:



Solution:
QUESTION: 20

Which of the following statements can be deduced about the stereochemistry of this compound?

organic-chemistry-questions-answers-stereochemistry-q10

Solution:

In identifying stereogenic centers, any quaternary or tertiary carbons would be a good place to look. There are no quaternary carbons, and all the tertiary carbons are part of a benzene ring structure.

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