WJEC CH4 June 2010

How did everyone find it? I though it was alright but there were some really awful questions that noone i know seemed to get. Like the three HBr isomers, think it was the two chiral isomers and 1 bromo. Didnt get it in the exam though....

I thought that exam was quite nice
Much better than January anyway, which I was totally unprepared for

I got 4 doubles bonds too

For the test between ethylamine and phenylamine what did everyone put?
I think the answer was adding nitrous acid and ethylamine would produce ammonia gas which would turn red litmus blue?

I didn't put that in the exam though, I said to add nitrous acid to turn ethylamine into ethanol and then add potassium dichromate and there would be a colour change from orange to green?
Think I'll get that?

I hate one marks questions especially in wjec because in chemistry they have half marks, which is ridiculous. I think I dropped marks everywhere pretty much :L

Aw I forgot to put 1,6-hexanediamine too!

Wait, why is everyone saying that the isomers were chiral?

My 3 isomers were 1,1-dibromobutane, 1,2-dibromobutane and 2,2-dibromobutane. Is that not right?

And if that was right, I said that if you analysed them by nuclear magnetic resonance, there would be 3 triplets for one, 4 for another, and 5 for the last, via the n+1 rule as there a 3, 4 and 5 protons on each isomer (respectively) that can 'see' another 2 protons.

What question was this for?
I'm hoping it's the polymer question about nylon, because I did NOT know the answer at all.

Ummmmmmmmmmmmmmmmmmmmmmmmmm, what happened to propanoic acid when you added soda lime? I didn't know what soda lime was, so I pretended it was CaCO3, and pretended CO2 was given off, leaving me with ethane.
What happened when you added CH3COCl? I wrote ethyalpropanoate.

Ummmmmmmmmmmmmm...
Oh, does anyone remember the systematic name for dettol? I don't think I did it right. I think I had 1,2-dimethyl4-chlorophenol. It doesn't look right.

How did you test between C and D? I wrote explicitly this C was a primary alcohol, D was secondary, but I don't know any tests. I guessed that when FeCl3 (iron III chloride) is added, primary alcohol solutions turn purple, while secondary alcohol solutions don't.

Wait, why is everyone saying that the isomers were chiral?

My 3 isomers were 1,1-dibromobutane, 1,2-dibromobutane and 2,2-dibromobutane. Is that not right?

And if that was right, I said that if you analysed them by nuclear magnetic resonance, there would be 3 triplets for one, 4 for another, and 5 for the last, via the n+1 rule as there a 3, 4 and 5 protons on each isomer (respectively) that can 'see' another 2 protons.



Yep, 4 double bonds.

I put add nitrous acid at <10 degrees celcius, aliphatic amine will give off N2, and I wrote that the other one "may give you a pretty colour".





What was an industrial use for ethanoic anhydride?
I said that it's used to turn morphine into heroin, and then wrote "(Pretty sure this is a bad thing though.)", so I don't know how that is going to go. It's true, but it's not really a use in industry.


Ummmmmmmmmmmmmmmmmmmmmmmmmm, what happened to propanoic acid when you added soda lime? I didn't know what soda lime was, so I pretended it was CaCO3, and pretended CO2 was given off, leaving me with ethane.
What happened when you added CH3COCl? I wrote ethyalpropanoate.

Ummmmmmmmmmmmmm...
Oh, does anyone remember the systematic name for dettol? I don't think I did it right. I think I had 1,2-dimethyl4-chlorophenol. It doesn't look right.

How did you test between C and D? I wrote explicitly this C was a primary alcohol, D was secondary, but I don't know any tests. I guessed that when FeCl3 (iron III chloride) is added, primary alcohol solutions turn purple, while secondary alcohol solutions don't.

Test between A and B was Tollen's right? Reagents silver nitrate and aqueous sodium hydroxide solution?

Ummmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm...
Well I don't know what else.


It was a really easy paper I think. Question 5 was a GIFT. Benzene structure, very easy (but I'm sure I've missed some points - I tried to talk about everything though, the p orbital overlap, p-pi blah blah blah...) and the rest of the question was quite simple (except for me using mass instead of moles to find percentage yield).
Oh, what is the attacking species in the nitration of benzene? I wrote HNO3, but I don't think that's right.

Ethanoic Anhydride is used for the synthesis of Aspirin.
I thought C had a double bond (hence being an EZ isomer- we had to draw two of them) and D didn't. :s
Also, Alcohol is polar covalent and will dissolve Phenol and FeCl3 will only give a purple complex with a phenolic group, not with a side chain aliphatic -OH group.

I thought the attacking species is the nitronium ion electrophile: +NO2? :s

I'm not so sure, my answers were riddled with mistakes and errors....