Edexcel Chemistry A2 Unit 5 ~ Wednesday 19th June 2013 (Now Closed) Watch

Poll: How pumped up are you for this exam?-(warning)-(bad jokes arene this poll!)
"Titanium-I'm not going to corrode (even at high temperatures)" (A*) (22)
16.67%
"Benzene's my middle name, give me the paper in a week and I'll ace it!" (A) (27)
20.45%
"Yeah, I'm fairly electrophillic (positively charged) about the exam" (B) (27)
20.45%
"I'm in the middle of the salt bridge, but I will pass-eventually" (C) (21)
15.91%
"I'm feeling rather electroNegative about this exam" (D) (18)
13.64%
"Benzene, what's that?" (E) (6)
4.55%
"Chemistry, what's that?" (F) (11)
8.33%
This discussion is closed.
posthumus
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(Original post by jojo1995)
green solution again
The Hydroxides make it a darker green...

...opposed to [Cr(H2O)6]2+ which is also green?

I read somewhere on the internet it was a grey precipitate though I've also read it's dark green !
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jojo1995
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(Original post by posthumus)
The Hydroxides make it a darker green...

...opposed to [Cr(H2O)6]2+ which is also green?

I read somewhere on the internet it was a grey precipitate though I've also read it's dark green !
Oh yeah I think your right I remeber there being one dark green ppt

(Original post by posthumus)
Omg that looks so hard, I'm worried now !

Is there a previous part to the question... isn't it the phenylamine ? :confused:

If not, I was going to say Tin Hydroxide... but realized that's not an organic compound
Yeah I thought tin hydroxide but yeah idts

No that's all to the q' hard stuff !

Thank you
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itsjordan
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#703
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(Original post by jojo1995)
*


see underlined stuff and bold stuff
Thank you!
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jojo1995
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#704
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Does anyone know the reagents and conditions required to change phenylethanol to benzoic acid ?

Thanks - really struggling w / this stuff
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jethacan
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(Original post by jojo1995)
Does anyone know the reagents and conditions required to change phenylethanol to benzoic acid ?

Thanks - really struggling w / this stuff
Heating with acidified potassium dichromate under reflux I think, it's from unit 4 for how carboxylic acid is prepared. Is that an exam question?
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LeaX
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#706
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Is there a reason why amines lose a hydrogen atom when reacting with acyl halides to form N-substituted amines whilst when amines react with halogenoalkanes they keep their alkyl group and two hydrogens?

Hope that question made sense haha.
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phaseshift
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#707
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I'm currently typing up some notes for the amino acids section whilst comparing the book to the syllabus (headache).

Is anyone else making a point of remembering/using examples such as poly(lactic acid) despite the fact they are not included as 'needed' in the syllabus which instead lists: "condensation polymerization for the formation of polyesters such as terylene and polyamides such as nylon and Kevlar" as required?

Opinions!
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posthumus
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(Original post by jojo1995)
Does anyone know the reagents and conditions required to change phenylethanol to benzoic acid ?

Thanks - really struggling w / this stuff
(Original post by jethacan)
Heating with acidified potassium dichromate under reflux I think, it's from unit 4 for how carboxylic acid is prepared. Is that an exam question?
Erm I believe an extra carbon is needed and the formula is C6H5COOH

I was thinking maybe CN- ions replacing the OH- to form H20 (or KOH for that matter)

using Unit 4 nitrile synthesis knowledge we can hydrolyze the C6H5CN as so:

C6H5CN + 2H20 + H+ ------> CH6H5COOH + NH4+

What do you guys think ??


(Original post by LeaX)
Is there a reason why amines lose a hydrogen atom when reacting with acyl halides to form N-substituted amines whilst when amines react with halogenoalkanes they keep their alkyl group and two hydrogens?

Hope that question made sense haha.
I see what you mean

True... there seems to be only one product, however if there is excess amine then it would react with the ammonium halide (product) in a reversible reaction to basically lose that hydrogen your talking about along with for example the Br- . Giving you 2 products... one you expected (with the NH group) & also a second product being made...

sorry I don't know what it's called when the amine gets a hydrogen and a halide but here's an example :

CH3CH2NH4Br


Hope that helps
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Weaselmoose
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The only reactions for phenol we need to learn are with bromine water and nitration right? And the fact that the oh group makes the phenol more reactive than both methyl and benzene?
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posthumus
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(Original post by Weaselmoose)
The only reactions for phenol we need to learn are with bromine water and nitration right? And the fact that the oh group makes the phenol more reactive than both methyl and benzene?
I haven't seen the spec but the reactions I see in the George Facer book:

Reaction with bromine
Nitration
Reaction with diazononium ions
Reaction with water
Reaction with sodium hydroxide
Reaction with sodium
Reaction with sodium hydrogen carbonate
Reaction with acid chlorides

That's a fair few but I guess some of those are the same with alcohols and are from previous units
So the only new thing you haven't mentioned and I think we need to know is the reaction with diazonium ions
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senz72
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Is there anyone willing to help on some complex questions?
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posthumus
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(Original post by HarryMWilliams)
I'm currently typing up some notes for the amino acids section whilst comparing the book to the syllabus (headache).

Is anyone else making a point of remembering/using examples such as poly(lactic acid) despite the fact they are not included as 'needed' in the syllabus which instead lists: "condensation polymerization for the formation of polyesters such as terylene and polyamides such as nylon and Kevlar" as required?

Opinions!
I've only made a note of the use of polyamides in Nylon in Kevlar due to the alignments of polymer chains and strong hydrogen bonding.

I haven't actually come across poly(lactic acid) and made no note of it ! And all the DNA stuff I skipped for that matter Although I think that has nothing to do with polymerization.
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posthumus
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(Original post by senz72)
Is there anyone willing to help on some complex questions?
Just post them here

Although myself still needs to go through everything & haven't really gotten onto revision really ! I will try and help...
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senz72
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Explain the following, including the appropriate equations in your answer:

i) Solid benzenediazonium chloride, C6H5--N+=NCL-(not has to be triple rather than double), is not usually isolated because it is explosive.

ii) Stable solutions of diazonium ions cannot be obtained from aliphatic primary amines like propylamine.
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jojo1995
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(Original post by jethacan)
Heating with acidified potassium dichromate under reflux I think, it's from unit 4 for how carboxylic acid is prepared. Is that an exam question?

thank you but as posthumus said there is an extra ch3 on the phenyl ethanol that needs to be removed

(Original post by posthumus)
Erm I believe an extra carbon is needed and the formula is C6H5COOH

I was thinking maybe CN- ions replacing the OH- to form H20 (or KOH for that matter)

using Unit 4 nitrile synthesis knowledge we can hydrolyze the C6H5CN as so:

C6H5CN + 2H20 + H+ ------> CH6H5COOH + NH4+

What do you guys think ?? yeah that reaction is correct, i always forget it --- its correct for your particular senario but i read the q wrong as usual




I see what you mean

True... there seems to be only one product, however if there is excess amine then it would react with the ammonium halide (product) in a reversible reaction to basically lose that hydrogen your talking about along with for example the Br- . Giving you 2 products... one you expected (with the NH group) & also a second product being made...

sorry I don't know what it's called when the amine gets a hydrogen and a halide but here's an example :

CH3CH2NH4Br


Hope that helps

thank you guys... but it was one step and the question was actually getting from phenylethanol to c6h5coona
- i think you would do the iodoform reaction therefore - do you think thats right ?

thank you so much again

edit ; jethan it was a question from a work sheet - not a exam q but .. could be
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jojo1995
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(Original post by senz72)
Explain the following, including the appropriate equations in your answer:

i) Solid benzenediazonium chloride, C6H5--N+=NCL-(not has to be triple rather than double), is not usually isolated because it is explosive.

ii) Stable solutions of diazonium ions cannot be obtained from aliphatic primary amines like propylamine.
WOAHHH are these exam question- i have absolutely no clue - all my easter holiday revision hasnt paid off
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phaseshift
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(Original post by posthumus)
I've only made a note of the use of polyamides in Nylon in Kevlar due to the alignments of polymer chains and strong hydrogen bonding.

I haven't actually come across poly(lactic acid) and made no note of it ! And all the DNA stuff I skipped for that matter Although I think that has nothing to do with polymerization.
Thats alright then.
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senz72
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(Original post by jojo1995)
WOAHHH are these exam question- i have absolutely no clue - all my easter holiday revision hasnt paid off
I don't think these questions will be asked but they were in my Hill and Hunt textbook. I've been stuck clueless for the past two hours trying to do these and some other questions.
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posthumus
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(Original post by senz72)
Explain the following, including the appropriate equations in your answer:

i) Solid benzenediazonium chloride, C6H5--N+=NCL-(not has to be triple rather than double), is not usually isolated because it is explosive.

ii) Stable solutions of diazonium ions cannot be obtained from aliphatic primary amines like propylamine.
Wow :/

I don't see how to approach the question for i) ... the temperature can't be above 10 degrees Celsius ? and cooled sodium nitrate may be used to maintain a temperature below 10 ?

Erm I am going to make an attempt on this and say that... if it is primary... there would be no extra alkyl groups to push electrons towards the nitrogen to make it less delta positive... because it's so delta positive it is a very powerful electrophile...

Do you have the answers ?
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YAH
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#720
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guys, how to reduce 4-nitrophenol to 4-aminophenol???
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