Q: Number of isomers which can be obtained theoretically on monochlorination of 2 -methylbutane is

1CH3−2CH2−1CH3∣3CH−4CH3has four types of H-atoms and gives four isomeric monochloro derivatives.

Q: An organic compound C4H8O, is found to be optically active. Which of the following could it be?

CH2=CH−CH(OH)−CH3 has a chiral carbon atom.

Q: Which of the following compounds will show metamerism?

Only C2H5−S−C2H5. The two metamers are CH3−S−CH2CH2CH3 and C2H5−S−C2H5.

Question 1

Number of isomers which can be obtained theoretically on monochlorination of 2 -methylbutane is

Accepted Answer

1CH3​−2CH2​−1CH3​∣​3CH​−4CH3​has four types of H-atoms and gives four isomeric monochloro derivatives.

Question 2

The molecular formula of diphenyl methaneis C13​H12​How many structural isomers are possible when one of the hydrogen is replaced by a chlorine atom?

Accepted Answer

Three in the ring and fourth on CH2​

Question 3

Diastereomers are

Accepted Answer

Diastereomers are stereoisomers that are non-superimposable and non mirror images. Cis-trans isomers are the examples of diastereomers.

Question 4

An organic compound C4​H8​O, is found to be optically active. Which of the following could it be?

Accepted Answer

CH2​=CH−CH(OH)−CH3​ has a chiral carbon atom.

Question 5

How many structural (including stereoisomers) isomers could be obtained by replacing one hydrogen of propene with chlorine?

Accepted Answer

When one hydrogen in propene is replaced with −Cl atom, four isomers (including stereoisomers) are possible.

Question 6

Which organic structure among the following is not an isomer of the compound?CH3​−CO−CH2​CH2​CH2​CH3​ ?

Accepted Answer

Structures given in option (b), (c) and (d) have the same molecular formula (C6​H12​O) as that of CH3​COCH2​CH2​CH2​CH3​ and are all isomers. The molecular formula of structure given in option (a) is C6​H10​O and it is not an isomer.

Question 7

The most stable conformation of ethylene glycol is

Accepted Answer

The most stable conformation of ethylene glycol is gauche conformation due to hydrogen bonding. Hence the right option is (B) gauche.

Question 8

In the reaction,CH3​CHO+HCN→CH3​CH(OH)CNa chiral centre is produced. This product would be

Accepted Answer

As during the reaction, a chiral carbon is created and further since the CN− ion can attack the planar aldehyde group both from the top and the bottom face of the aldehyde group with equal ease, therefore, a 50:50 mixture of the two enantiomers, that is, a racemic mixture is obtained.

Question 9

Which of the following compounds will show metamerism?

Accepted Answer

Only C2​H5​−S−C2​H5​. The two metamers are CH3​−S−CH2​CH2​CH3​ and C2​H5​−S−C2​H5​.

Question 10

Fischer projection indicates:

Accepted Answer

In fischer projections, horizontal substituents are above the plane.

Question 11

Which of the following has zero dipole moment?

Accepted Answer

Trans-2-butene has zero dipole moment.

Question 12

The total number of isomers for C4​H8​ is

Accepted Answer

Six.These are:1-butene, trans-2-butene, cis-2-butene, 2-methylpropene, cyclobutane and methyl-cyclopropane.

Question 13

2,3 -dimethyl hexane contains .... tertiary .... secondary and ….. primary carbon atoms, respectively.

Accepted Answer

Above is the structure of 2,3 dimethyl hexane. We can clearly see there are 2 tertiary, 2 secondary and 4 primary carbon atoms.

Question 14

The number of enantiomers of the compound CH3​CHBrCHBrCOOH is

Accepted Answer

The compound CH3​∗CHBr∗CHBrCOOH contains two dissimilar chiral carbon atoms and hence 22=4 enantiomers are possible.

Question 15

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

Accepted Answer

Boat conformation of cyclohexane has two types of destabilizing interactions, that is, eclipsing and flagpole-flagpole. Out of these eclipsing interactions are the most destabilizing.

Question 16

Which of the following has zero dipole moment?

Accepted Answer

Trans-1,2-dichloroethene has zero dipole moment.

Question 17

The Baeyer's angle strain is expected to be maximum in

Accepted Answer

As the size of the ring increases, the internal angle increases accordingly. As a result, the deviation from the tetrahedral angle and the angle strain increases as the size of the ring increases. Thus, planar cyclodecane is expected to have the maximum angle strain.

Question 18

(+)-Mandelic acid has a specific rotation of +158∘. What would be the observed specific rotation of a mixture of 25% (-)-mandelic acid and 75% (+)-mandelic acid?

Accepted Answer

Specific rotation of the mixture =(75/100)(+158∘)+(25/100)(−158∘)=+79∘

Question 19

The number of geometrical isomers of CH3​CH=CH−CH=CH−CH=CHCl is

Accepted Answer

As both the carbon atoms of each of the three double bonds are differently substituted, therefore, 23=8 geometrical isomers are possible.

Question 20

The number of isomers possible for C7​H8​O is

Accepted Answer

These are: benzyl alcohol, anisole, o−,m and p-cresols (that is, methyl phenols).

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Solutions for Organic Chemistry for the IIT JEE by Atul Singhal

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