Test Level 1: Previous Year Questions Isomerism - JEE MCQ

Stereoisomerism is defined as two molecules which have the same molecular formula but the atoms are arranged differently in space. The other major form of stereoisomerism is optical isomerism. Optical isomers arise when a chiral carbon is present, this is a carbon atom attached to four different groups.

The correct answer is Option B.
Conditions of geometrical isomerism :
(I) Geometrical isomerism arises due to the presence of a double bond or a ring structure

Due to the rigidity of double bonds or the ring structure the molecules exist in two or more orientations. This rigidity to rotation is described as restricted rotation / hindered rotation / no rotation.

(II) Different groups should be attached at each doubly bonded atom.

(III) Groups responsible to show geometrical isomerism must be nearly in the same plane.
 
CH₃CH₂CH=CH₂ , can’t show geometric isomerism because it does not satisfy the above condition.

Both are the same,
 

A racemic mixture consists of chiral molecules, but it has no net optical activity. The process by which a racemic mixture is formed from chiral materials is called racemization. One way to do this is to mix equal amounts of enantiomeric substance.

The correct answer is option A
From all the compounds in the question only  1,1-dichloro-1-pentene has no geometrical isomer(no cis-trans).’cis’ form or ‘trans’ form occour when some groups placed in two different doubly bonded carbon in same side (cis form) or in opposite side (trans form).
Here two ‘Cl’ groups present in one carbon. Hence here is no possibility to form any geometrical isomer.

The correct answer is option A
Chiral carbon atoms are also referred to as 'stereogenic carbons' or 'asymmetrical carbon atoms'. Compound 1 has a chiral carbon center, because it is attached to four different groups (W, X, Y and Z).
 

Chiral compounds are those which have one chiral centre. All four atoms or groups attached to carbon are different. 
Only (i) and (ii) are chiral carbons.

The correct answer is option A
1-chloro-pentane
CH₃−CH₂−CH₂−CH₂−CH₂Cl
As it does not contain a chiral centre so it is optically inactive (not chiral)compound.

Gauche conformation is comparatively more stable due to hydrogen linkage in between F and H (atO−atom), hence order is Eclipse, Anti (staggered), Gauche.

1 stereo center.
The central carbon is a chiral carbon.
So, it is optically active.
Optically active compounds rotate the plane of polarised light.

Twist boat form is chiral as it lacks plane of symmetry

Four different groups attached to chiral center are arranged in decreasing order of priority. The lowest priority group is placed below the plane of paper. When the remaining 3 groups in decreasing order of priority are in clockwise direction, the configuration is R and when the direction is counterclockwise, the configuration is S.

The alkene that exhibits geometrical isomerism is. 2-Butene may exist as cis and trans isomers. The cis-isomer has the two methyl groups on the same side and the trans-isomer has the two methyl groups on opposite sides. Due to restricted rotation around double bond it exhibits geometrical isomerism.

About the double bond, two geometrical isomers are possible and the compound is having one chiral carbon.

The correct answer is 3-methyl-1-pentene because it has one chiral centre.

The correct answer is option A

Chlorination at C-2 and C-4 produces no chiral compound.Hence (A) is the correct answer.