Aqa chem4 15th june 2011 (resit) thread

Original post by FristyKino

I've got 5 exams left :frown:

(

I need ABB for leeds :mad:

But I think max I can get is BBB if i do well in all my exams.
Was hoping for A in chemistry - And only way I could do that is if they let me resit unit 2 - + getting straight A's in Unit 4 and 5.
Not too worried about unit 5 - unit 4 im worried about.
But after people sat the unit 2 in may and came out they were all happy - that was literally the most depressing day of my 2 years at college :angry:

So hopefully if i do get the 3B's ( :biggrin:

) then maybe, just maybe leeds might let me in :biggrin:

I had applied for biochemistry in Sheffield and sheffield hallam. Sheffield rejected me and I didnt want to go to sheffield hallam (:

Im guessing you're looking at kind of the same grades?

Oh I see. I think Leeds might be lenient (especially as it's your firm), it totally depends on the number of people who miss their offer. I wasn't happy with my A-level grades as I knew I could have done significantly better, so I decided to take a gap year and resit the whole of chemistry (minus PSA) in the hope an an A/A* grade. My offer is ABC - an A in Chemistry so I'm hoping to get it. I missed my firm choice and decided not to go into clearing because I didn't want to sell myself short. So here I am.

What accommodation have you gone for - I've gone for Oxley.

Reply 81

Original post by T-Toe

Thank you , what about converting amide to nitrile (and visa versa)?

Out of curiosity why do you want to know this?

As far as I'm aware the only knowledge you need for unit 4 that involves organic synthesis with nitriles is its reduction into amines using hydrogen and a nickel catalyst (or LiAlH4 in dry ether) to produce amines, e.g:

CH3CH2CN + 2H2 --> CH3CH2CH2NH2

Is this what you meant?

The only other area of synthesis they crop up in is the Nucleophilic Addition of Aldehydes to form hydroxynitriles.

CH3CHO + HCN --> CH3CH(OH)CN

If you were just wondering, it is possible to convert amides into nitriles through dehydration (see http://www.tutorvista.com/content/chemistry/chemistry-iv/organic-compounds/dehydration.php) and vice vera by hydration.

Reply 82

Original post by jimmy303

Out of curiosity why do you want to know this?

As far as I'm aware the only knowledge you need for unit 4 that involves organic synthesis with nitriles is its reduction into amines using hydrogen and a nickel catalyst (or LiAlH4 in dry ether) to produce amines, e.g:

CH3CH2CN + 2H2 --> CH3CH2CH2NH2

Is this what you meant?

The only other area of synthesis they crop up in is the Nucleophilic Addition of Aldehydes to form hydroxynitriles.

CH3CHO + HCN --> CH3CH(OH)CN

If you were just wondering, it is possible to convert amides into nitriles through dehydration (see http://www.tutorvista.com/content/chemistry/chemistry-iv/organic-compounds/dehydration.php) and vice vera by hydration.

Thanks. The A2 Nelsons text book - it's mentioned on the inter-relationships between functional groups, page 125. I thought it was worth knowing.

Reply 83

Original post by jimmy303

Out of curiosity why do you want to know this?

As far as I'm aware the only knowledge you need for unit 4 that involves organic synthesis with nitriles is its reduction into amines using hydrogen and a nickel catalyst (or LiAlH4 in dry ether) to produce amines, e.g:

CH3CH2CN + 2H2 --> CH3CH2CH2NH2

Is this what you meant?

The only other area of synthesis they crop up in is the Nucleophilic Addition of Aldehydes to form hydroxynitriles.

CH3CHO + HCN --> CH3CH(OH)CN

If you were just wondering, it is possible to convert amides into nitriles through dehydration (see http://www.tutorvista.com/content/chemistry/chemistry-iv/organic-compounds/dehydration.php) and vice vera by hydration.

I'm pretty sure we need to know how to convert amines to amides.

Reply 84

Original post by T-Toe

Thanks. The A2 Nelsons text book - it's mentioned on the inter-relationships between functional groups, page 125. I thought it was worth knowing.

Ah fair enough, never did anyone harm to know more that what's needed I suppose :tongue:

Never used that text book :redface:

Reply 85

Original post by jimmy303

Ah fair enough, never did anyone harm to know more that what's needed I suppose :tongue:

Never used that text book :redface:

What did you use, just the revision guide?

Reply 86

Original post by FristyKino

I'm pretty sure we need to know how to convert amines to amides.

T-Toe32033335

x

True enough, I almost included this in my original reply.

Nitriles --> Amines --> Amides.

If that's what you were asking for then sorry for confusing you T-Toe :colondollar:

Just assumed you meant a direct conversion.

Reply 87

Original post by T-Toe

What did you use, just the revision guide?

CGP Revision guide, various websites, and a Philip Allan revision book. Don't really trust the Nelson Thornes books after all the irrelevant rubbish the one for biology AS I bought included (just my opinion though!)

Reply 88

Original post by jimmy303

True enough, I almost included this in my original reply.

Nitriles --> Amines --> Amides.

If that's what you were asking for then sorry for confusing you T-Toe :colondollar:

Just assumed you meant a direct conversion.

No, I meant the direct conversion. Now we're on this topic how do we convert amines to amides? AQA makes no mention of this :confused:

In fact amides are rarely mentioned.

(edited 12 years ago)

Reply 89

dolmio

7

is there a chem 5 thread anywhere...?

Reply 90

T-Toe

x

From the AQA spec:

Acylation:
know the reactions of water, alcohols, ammonia and primary amines with acyl chlorides and acid anhydrides.
understand the mechanism of nucleophilic addition–elimination reactions between water, alcohols, ammonia and primary amines with acyl chloride

It doesn't say what the products of these reactions are which is pretty mean but with ammonia you get normal amides and with amines you get N-substituted amides.

See page 20 onwards of the notes from http://www.a-levelchemistry.co.uk/AQA%20Chemistry/AQA%20A2%20Chemistry/Unit%204/4.5%20Compounds%20Containing%20the%20Carbonyl%20Group/4.5%20Compounds%20Containing%20the%20Carbonyl%20Group.htm.

That will explain it better than I can and gives the mechanisms, but for now i'll give you some examples:

With Ammonia:
CH3COCL + 2NH3 --> CH3CONH2 + NH4+CL-
(Ethanamide and ammonium chloride produced)

(CH3CO)2O + 2NH3 --> CH3CONH2 + CH3COO-NH4+
(Ethanamide and Ammonium ethanoate produced)

With Amines:
CH3COCL + 2CH3NH2 -->CH3CONHCH3 + CH3NH3+CL-
(N-methylethanamide and methylammonium chloride produced)

(CH3CO)2O + 2CH3NH2 --> CH3CONHCH3 + CH3COO-CH3NH3+
(N-methylethanamide and methylammonium ethanoate produced).

amides can also be produced by condensation (removal of a water molecule) between an amine and a carboxylic acids, e.g. Nylon- 6,6, which is covered under polymers.

:smile:

dolmio

is there a chem 5 thread anywhere...?

The best one I could find was http://www.thestudentroom.co.uk/showthread.php?t=1588457&highlight=chem+5+aqa. Enjoy! :tongue:

Reply 91

dolmio

7

Original post by Arcanine

Chill the **** out. Revise and you'll be fine. I find these to be somewhat helpful.

Hey, thank you very much for the notes - they're really helpful! I noticed you posted notes for all the chapters but chapter 11, do you have the notes for this chapter? please :smile:

Reply 92

Arcanine

14

Original post by dolmio

Hey, thank you very much for the notes - they're really helpful! I noticed you posted notes for all the chapters but chapter 11, do you have the notes for this chapter? please :smile:

See post 66.

Reply 93

Does anyone have the question paper and markscheme for Jan 2011?

Reply 94

jwest

anyone got a copy of the examiners report from the jan 11 exam? had a little hunt around on the internet but cant seem to find it anywhere...

Reply 95

EavieQu

Hi, where does K2Cr2O7 come up and what is it used for??

Reply 96

Zakir

Original post by EavieQu

Hi, where does K2Cr2O7 come up and what is it used for??

hey..

its an oxidising agent, can be used to oxidise aldehydes to primary alcohols and a ketone to secondary alcohols.

it'll probably come up if theres a question to do with aldehydes and ketones i reckon...

(edited 12 years ago)

Reply 97

Original post by Zakir

hey..

its an oxidising agent, can be used to reduce aldehydes to primary alcohols and a ketone to secondary alcohols.

it'll probably come up if theres a question to do with aldehydes and ketones i reckon...

Oxidising agents oxidise other things (and get reduced themselves)
Potassium dichromate oxidises Primary alcohols to aldehydes and secondary alcohols to ketones.

Something like NaBH4 would be used to reduce them

(edited 12 years ago)

Reply 98

lfc4lyf

5

i was just doing a past paper and came across a moles question which seems impossible to do ! its from the jan 2005 paper (old spec) can anybody explain how i can get the answer please !!!
its question 5ai and the answers are 0.40 for c2f4 and 0.80 for hcl

http://www.thomas-reddington.com/uploads/7/7/8/3/778329/chem_u4_old_qp_jan_2005.pdf

Reply 99