Isomerism - 1 - JEE MCQ

C₆H₁₄ indicates saturated hydrocarbon i.e., an alkane. There are 5 chain isomers possible with this formula i.e., one linear, two monosubstituted, two distubstituted. Here are the isomers of C₆H₁₄ 

• When two or more compounds have the same molecular formula but the different position of functional groups are substituents, they are called positional isomers and the phenomenon is called position isomerism.
• Here 2-chloropropane and 1-chloropropane differ in position so they exhibit position isomerism.

The isomer of ethanol(CH₃-CH₂-OH) is dimethyl ether(CH₃-O-CH₃). This is a functional isomer of ethanol.

Explanation:

• Functional isomers are the ones with the same molecular formula but different functional groups.
• The molecular formula for dimethyl ether is C2H6O similar to ethanol.
• Dimethyl ether has the structural formula CH3OCH3 and ethanol has the structural formula CH3CH2OH.
• Therefore, dimethyl ether is the functional isomer of ethanol as both have the same molecular formula but one is ether and the other is alcohol. 

Two molecules are described as stereoisomers if they are made of the same atoms connected in the same sequence, but the atoms are positioned differently in space.
Additional Information: Stereoisomers can be subdivided into: 
(i) Optical isomers: Optical isomers are those two compounds with the same chemical formula such that their mirror images are not superimposable on each other. Depending on the direction they rotate the plane of polarised light in a polarimeter, we have two forms of optical isomers. They are:

• Dextro Isomer: This rotates to right.
• Laevo Isomer: This rotates to left.

An example is butan-2-ol. It has four different groups attached to its second carbon atom.

(ii) Geometric isomers: In the case of disubstituted complexes, the substituted groups could either be adjacent or opposite to each other. This leads to geometric isomerism. Thus, we can prepare square planar complexes such as [Pt(NH₃)₄Cl₂]  in two forms, cis and trans. When the chlorine atoms are adjacent to each other, we get the cis form. When two chlorine atoms are opposite, we get the trans-form.

The specific rotation is given by the expression observed rotation/length X density, here as observed rotation is given as 3x and its length is given as x, while the density is 3/y, the specific rotation equals 3x/x(y/3) = y.

Geometrical isomers have different spatial arrangement.

Z-isomers have senior groups on same side.

Self explanatory

Self explanatory

According to CIP rule first decide the seniority of groups and than decide the configuration.

Meso CH₃ – CHCl – CHCl – CH₃ have equal polarity in opposite direction so cancel out.

9

Aldehyde and Ketone are functional isomers.

Diple moment, boiling point and water solubility are greater for II(cis) but melting point is greater for I(trans) isomer.

becuase of effictuis facking in lattice