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

In the specification it says 'describe and carry out, where appropriate, the preparation of a compound, eg cholesteryl benzoate (a liquid crystal) and of methyl 3-nitrobenzoate, requiring some of the following techniques...' Do we need to know how to make cholesteryl benzoate and methyl 3-nitrobenzoate or just how to carry out the different techniques??

Guys a question!

Can Ecell be negative?
Also Is H20 ligand smaller than OH-?

If not why is it Zn(H20)6 and Zn(OH)4? Why is there a decrease in coordination?

I'm so going to fail!

no no just 3. The one marked with same colour are one H environment

if u look at the one which is projectiong out its in same environment as the one just below is coz they both are bonded to same group. Again if u look at another CH2 at the top plane t it is bonded to same groups as the one which is at the corner of the plane below. so they are in same environment

yes it can be. umm I think it is bigger than OH-
there is no decrease in coordination number sometimes they write [Zn(OH)4(H2O)2]2+ as [Zn(OH)4]2+

thank you there was meant to be a cl on the last carbon ... so that would mean there were 5 right ?



yeah i see that now thank you for all your help .... but why arent all 4 ch2s in the same h enviroment- thay are all attached to the same groups ?

Does that mean it's partial ligand exchange? Why isn't it [Zn(Oh)6]4-?

Thanks.

lol! sorry! then yeah 5 environments
umm I think its coz those CH2s are not bonded to each other.

After u do steam distillation u have product with mixture of water and phenylamine right?
u wanna get rid of water so what u do is add NaCl and keep in separating funnel. I think aq layer will be below and organic layer at the top so u can get rid of aq layer by opening the tap. After than u have organic layer left which will still have water in it. So what u need to do next is add anhydrous Na2CO3 why this and not CaCl2 is coz CaCl2 and magnesium sulphate will react with phenylamine. So now water will be removed but then again u have sodium carbonate in ur product so u decant the product and then distil the solution to get phenylamine in pure form.
lol I think I explained more than what u asked for

thank you

Once again perfect explanation thank you so much, so adding nacl will make phenyl amine not dissolve in water and thats how the 2 layers form in the separating funnel right? but how come still some water left in the organic layer if tap was opened for aqueous layer?

could someone please help with with jan 2012 question 10 and 11 in the multiple choice section.

for 10, i know the answer won't be A or C but i don't understand how you know which out of ch3coch3 and ch3cocl won't react? the answer is B.

for 11, i understand how they got the answer but i'm just wondering why doesn't phenylamine undergo sulfonation with dilute sulfuric acid? cos wouldn't the lone pair on N activate the ring? (similarly to how phenol reacts)

thanks

After u do steam distillation u have product with mixture of water and phenylamine right?
u wanna get rid of water so what u do is add NaCl and keep in separating funnel. I think aq layer will be below and organic layer at the top so u can get rid of aq layer by opening the tap. After than u have organic layer left which will still have water in it. So what u need to do next is add anhydrous Na2CO3 why this and not CaCl2 is coz CaCl2 and magnesium sulphate will react with phenylamine. So now water will be removed but then again u have sodium carbonate in ur product so u decant the product and then distil the solution to get phenylamine in pure form.
lol I think I explained more than what u asked for

Do we have to know all of this and the last post for the exam?!

yes we do
what we need to know is how steam distillation works

Hmm I'd take a gamble and not bother then, a big steam distillation question already came up a couple of years ago so they'll probably do something on recrystallisation/reflux/fractional distillation.

Also we don't need to know about all that stuff you said after the steam distillation?

The C=O in esters does not react with Brady's reagent right?

Nope they don't