WCH11 June 2022

15.​​ A hydrocarbon X has a molar mass of 98gmol−1​​ . When a sample of X is shaken with bromine water, the colour of the bromine water does not change. Which of these could be the structure of X?

ANSWER

Analysis of Option/Explanation

The student should identify first that for which structure the Mr​​ is 98. Upon analysis it is found that Mr​​ of Option A structure is 100, Mr​​ of​​ option B structure is 114, Mr​​ of Option C and Option D structure is 98. Hence, option A and B is cannot be the answer.

Now, other important thing which is mentioned in the question is that “When a sample of X is shaken with bromine water, the color of the bromine water does not change” i.e. the structure does not have C=C double bond. Therefore Option D is the correct answer which fulfills condition given in the question i.e. Mr =100 and absence of C=C double bond which does not lead to color change.