Question

a. How many isomers are possible for the compound with the molecular formula C₄H₈? Draw the electron dot structure of branched chain isomer. 

b. How will you prove that C₄H₈ and C₅H₁₀ are homologues?

OR 

A carbon compound ‘A’ having melting point 156K and boiling point 351K, with molecular formula C₂H₆O is soluble in water in all proportions.

a. Identify ‘A’ and draw its electron dot structure. 

b. Give the molecular formulae of any two homologues of ‘A’.

Answer 1

(a) Four

4 isomers are Possible with C₄H₈ as shown below

Isomers are

Organic Compounds having similar molecular formula but different structures

It is possible only in hydrocarbons having 4 or more carbon atoms

1-butene, cis-2-butene, trans-2-butene, and isobutylene.

Branched Chain Isomer

In this case,3 carbon atom are put in straight chain

Fourth Carbon atom is put in side as shown below

(b) C₄H₈ and C₅H₁₀ are homologues 

as they differ in

● “- CH ₂ -”

● differ in 14u molecular mass

● Same functional group

● Same general formula 

Homologues are group of chemical compounds which have similar structure and similar chemical properties and successive compounds differ by CH₂

Example of Homologues Series of Alkenes

Ethene C₂H₄

Propene C₃H₆

Butene C₄H₈

Pentene C₅H₁₀

Hexene C₆H₁₂

It can be seen that

Difference between C₄H₈ and C₅H₁₀ is CH₂

Also these 2 share similar structure and chemical properties (both are alkenes)

Hence these are homologues.

(a) Ethanol; C₂H₅OH

Ethanol is a colourless liquid having boiling point 351k and melting point 156k

Also it is soluble in water

Its formula is C₂H₅ OH

Electron Dot Structure of Ethanol is as follows

(b) (Ethanol is an alcohol)

Examples of Alcohols

Note

All the above are homologues

Homologues are group of chemical compounds which have similar structure and similar chemical properties and successive compounds differ by CH₂

We can say that homologues of ethanol are

Answer 2

a. Four

b. C₄H₈ and C₅H₁₀ are homologues

as they differ in 

● “- CH₂-” 

● differ in 14u molecular mass 

● Same functional group 

● Same general formula

OR 

a. Ethanol; C₂H₅OH

b. CH₃OH and C₃H₇OH are homologues of ethanol

OR 

CH₄O and C₃H₈O