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OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016)

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Reply 960

Major Wilson

I got methylpropanoic acid?

Reply 961

Tyler213

Original post by 4nonymous

Yh it would. Also I think for yield it was 67.4%
As for the last question 43 peak does work with butanoic acid because its (CH3CH2CH2)+ ? Although I aint sure

Fair enough. But how would you get a secondary carbocation in butanoic acid?

Reply 962

Firenze26

Original post by Major Wilson

I got methylpropanoic acid?

😐...

Dang it.

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Reply 963

4nonymous

Original post by ronnydandam

it was 'in the first 200 secs' not at 200 secs I think

I thought it said at. LOL we both "think"

Original post by asinghj

Check chemistry textbook page 148

CBA - its done with now so who cares. Just glad chem is over with.

Reply 964

11234

Did anyone say it was flammable so heat with electric heater under reflux

Reply 965

LordStark

Original post by Firenze26

Please tell me the last one about the mass spec question was Butanoic acid

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I'm pretty sure it was. All the peaks (including 43) work fine with butanoic acid. I thought the mention of a secondary carbocation was just useless information - there isn't carbocations present in carboxylic acids anyway, only during reaction mechanisms right?

Reply 966

11234

I put 67 percent to 2 sig figs do I lose any marks

Reply 967

Riadiram

Original post by LordStark

I got methylbutanoic acid because I thought it would be able to make a secondary carbocation, but I dunno

Reply 968

Abby3112

Original post by 11234

Did anyone say it was flammable so heat with electric heater under reflux

That's the exact thing I wrote :smile:

let's hope it's right! Haha

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Reply 969

asinghj

Original post by torilee

I got that as well. :h:

I think that's the correct answer, but they'll probably give marks for butanoic acid as well, because it is an isomer of butanoic acid after all

I think butanoic acid would be 5/6 marks because it clearly mentioned secondary carbonation

Reply 970

Vanilla Poison

Original post by Awsomedude

Mg was ionic I swear, it forms ionic bonds, not metllaic bonds.

Wasn't talking about MgO, just the metal itself.

Reply 971

usmanahmed321

it was butanoic aCid
you had TO times the EF C2H4O by two to get C4H802 OF WHICH THE MR WAS 88
THERE WAS ALSO AN M/Z PEAK AT 88 SUGGESTING IT WAS BUTANOIC ACID
IT COULDNT HAVE BEEN C2H40 SIMPLY BECUASE THAT ISNT A CARBOXYLIC ACID
THE IR SPEC CLEARLY INDICATED IT WAS A C ACID
THE MAS SPEC ALSO SAID THE MOST INTENSE PEAK WAS CAUSED BY A CARBOCATION WHICH WAS AT 43 OR 44
SO THE MR WAS 88
anyone agree?

Reply 972

4nonymous

Original post by Tyler213

Fair enough. But how would you get a secondary carbocation in butanoic acid?

Im not sure. I think it was methy-propanoic but I was just showing that you can have butanoic with that 43 m/z
I put butanoic but oh well

Reply 973

Awsomedude

Original post by 4nonymous

Its metallic, ionic is between + and - ions metallic is between the + mg2+ ion and the delocalised electrons

that's 2 marks down

Reply 974

Tyler213

A secondary carbocation meant that the positive charge had to be on a carbon that had 2 other carbons attached. So its not useless information, its actually vital.