Alcohols, isomers etc.

I'm really stuck on this question, any help would be really appreciated! I'm stuck on part iv - i think I've done all the other parts correctly. Thanks!


(b) Four unsaturated isomeric hydrocarbons have a relative a relative molecular mass of 56 and the following percentage composition by mass: C, 85.7%; H, 14.3%. These four isomeric hydrocarbons can be made to react with steam forming alcohols. One of the alcohols, T, does not react with acidified potassium dichromate(IV) K2Cr2O7.

(i) Calculate the molecular formula of the four isomers.​ ​ [3]

(ii) Deduce the structure of the four isomers.​ ​ [4]

(iii) Deduce all the alcohols that could be formed from the four isomers. ​ ​ [4]

(IV) Identify the alcohol T and deduce which of the isomers in (b)(ii) reacted with steam to produce it.




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So you know the percentage composition and with this you can find the empirical formula. Then you can find out the molecular formula by matching it with the molecular mass. After you can draw out the different isomers because you'll know the number of C and H atoms in the molecule. One of the isomers will form a secondary or tertiary alcohol as it doesn't react with acidified dichromate to form an aldehyde.

No,secondary alcohols oxidise to ketones, it must be a tertiary alcohol-she just needs to find a way to branch it that matches molecular formula

Sorry, you're correct. I'm just too used to seeing acidified dichromate used to form carboxylic acids aha

Thats what a2 organic does to you- you forget the AS reactions

aha too true, can't wait to get chem over and done with

Yes its a stress but i need it for my course-what did you apply for?

I applied for medicine, yourself?

as did i, what unis?

I applied to Liverpool, Sheffield, Exeter and Plymouth and got an offer from plymouth and rejection from the rest. You?

imperial, UCL, cambridge and st george`s- offer from UCL and rejected from rest- news flash medicine is competitive

Wayyyyy too competitive aha