URGENT A/S Chemistry Org: Reactions & Isomers

Hi, I am stuck on the following:

Reduction of a branched alkene A with hydrogen formed a compound B. On analysis, B had the composition by mass of C, 82.8%; H, 17.2% (Mr = 58). Reaction of A with steam in the presence of a catalyst produced a mixture of two isomers C and D.

Identify possible structures for compounds A-D. Your answer should show all working and include strucutral formulae for each structure and equation for each reaction. [9 marks]

I have calculated the empirical formula of B = C2H5 and the molecular formula of B = C4H10.

Reply 1

Chicken

Ok, well you've started correctly by working out B, then you have to work backwards for A. As B is Butane, and A is a branched alkene, I think A is methylpropene. Would you agree with that?

Reply 2

supreme

according to the book, B is (CH3)2CHCH3 I am so confused ! :eek:

Reply 3

Chicken

supreme

according to the book, B is (CH3)2CHCH3 I am so confused ! :eek:

Ok sorry I was forgetting A was branched, which makes B methylpropane, but its kinda hard to draw it on here! Have you looked up the reactions of alkenes with steam, which will help you find C and D?

Reply 4

supreme

Thanks I will look up the reactions and see if I understand :smile:

Reply 5

Chicken

If you want I can write it on a piece of paper for you and scan it and post it up here so you can see what the compounds should look like? You should get an alcohol, which has 2 isomers.

Reply 6

supreme

If you could that would be helpful :smile:

Reply 7

karen_uk

(CH3)2CHCH3 is the same as C4H10 but (CH3)2CHCH3 is structured. (CH3)2 is branched off the C on the CH part if u get wot i mean!!

alkenes react with steam to produce alchohols. the catalyst is phosphoric acid. ths process is called direct hydration. so maybe 1 of ur isomers is an alcohol

Reply 8

Chicken

Ok, here it is, i've had to resize it really small so it'll fit as an attachment so you might have to fiddle with it before you're able to read it!

I haven't included reaction equations on it though.

If you can't read it I'll make it big and send it to you by email, if you want.