[amy barnes]

anyone got markscheme for jan 2012 paper f324?? I really wanna mark my paper but cant seem to find the mark scheme anywhere :/

[Smiley Face :)]

(Original post by browb003)
Hi everyone, I've made some past paper question booklets that I can share with you

Also I've crudely put together a booklet on proton NMR (too big to upload to TSR )
NMR Booklet: http://www.datafilehost.com/download-6e281dbf.html
Mark scheme: http://www.datafilehost.com/download-241f9cf2.html

You got any for F325 by any chance??

[Smiley Face :)]

(Original post by Smiley Face :))
You got any for F325 by any chance??

Nevermind, just found it

[1234girl]

hey just wanted to ask if we need to know any other diazotisation/coupling reactions, except for phenylamine?

[Fatima0065]

Can anyone tell me if this is all we need to know for kekule's structure...
1) Benezen's has an enthalphy of hyrdogention of 208 kjmol///which is less thna expected so benzene is more stable than thought
2) Benzene can only recat with Bromine in the presence of a halogen acrrier catalyst
3) The benzene molecule is not symterical as the single c-c bonds are longer thaan the c=c double bonds

3marks worht? is isit right...if you want to add anythig please do

[splendidsun]

How many different proton environments are there in C6H5CH2CH3?

[racheatworld]

(Original post by splendidsun)
How many different proton environments are there in C6H5CH2CH3?

It has 5, as shown by my diagram below:

Carbon 1 in the benzene ring does not count as a proton environment as there are no H's attached to carbon 1.

[racheatworld]

(Original post by Fatima0065)
Can anyone tell me if this is all we need to know for kekule's structure...
1) Benezen's has an enthalphy of hyrdogention of 208 kjmol///which is less thna expected so benzene is more stable than thought
2) Benzene can only recat with Bromine in the presence of a halogen acrrier catalyst
3) The benzene molecule is not symterical as the single c-c bonds are longer thaan the c=c double bonds

3marks worht? is isit right...if you want to add anythig please do

That's right! (Well it is all I have in my notes).

• In Kekule's structure, the C-C bonds are longer than C=C bonds, however in benzene all bonds are the same length.
• In Kekule's structure, the compound should have an enthalpy of hydrogenation of -360 kJmol-1, however benzene has an enthalpy of hydrogenation of higher value at -208kJmol-1. This means that benzene is more stable than Kekule's structure as more energy is required to hydrogenate it.
• Kekule's structure should be able to undergo addition reactions, for example reacting with Br2 (aq). However Benzene undergoes substitution reactions and will only react with Br2 (aq) in the presence of a halogen carrier catalyst.

[Fatima0065]

(Original post by racheatworld)
That's right! (Well it is all I have in my notes).

• In Kekule's structure, the C-C bonds are longer than C=C bonds, however in benzene all bonds are the same length.
• In Kekule's structure, the compound should have an enthalpy of hydrogenation of -360 kJmol-1, however benzene has an enthalpy of hydrogenation of higher value at -208kJmol-1. This means that benzene is more stable than Kekule's structure as more energy is required to hydrogenate it.
• Kekule's structure should be able to undergo addition reactions, for example reacting with Br2 (aq). However Benzene undergoes substitution reactions and will only react with Br2 (aq) in the presence of a halogen carrier catalyst.

Thanks...makes more sense when someone else says it lol Do you wana start sharing notes etc and start revsiing properly ?

[Fatima0065]

Can anyone put up the legacy papers from 2008 up please, because for some reason my computer won't download the zip files. Thankyou

[splendidsun]

(Original post by racheatworld)
It has 5, as shown by my diagram below:

Carbon 1 in the benzene ring does not count as a proton environment as there are no H's attached to carbon 1.

Thanks, thought so but according to the black textbook answer section, it forms 3 peaks...I'll just take it to be a typo

[racheatworld]

(Original post by splendidsun)
Thanks, thought so but according to the black textbook answer section, it forms 3 peaks...I'll just take it to be a typo

3 peaks for proton environments? Don't think the book is right. Maybe they are talking about C¹³ NMR?

[splendidsun]

(Original post by racheatworld)
3 peaks for proton environments? Don't think the book is right. Maybe they are talking about C¹³ NMR?

Nope, definitely proton NMR, and all benzene ring protons are taken to be in the same environment...which doesn't seem right at all

[racheatworld]

(Original post by splendidsun)
Nope, definitely proton NMR, and all benzene ring protons are taken to be in the same environment...which doesn't seem right at all

No that definitely is not right and is not what I have been taught, both in the OCR textbook and in past exam papers.

[TourettesUnicorn]

(Original post by browb003)
Hi everyone, I've made some past paper question booklets that I can share with you

Also I've crudely put together a booklet on proton NMR (too big to upload to TSR )
NMR Booklet: http://www.datafilehost.com/download-6e281dbf.html
Mark scheme: http://www.datafilehost.com/download-241f9cf2.html

I applaud you sir.

[moh.alt]

Heres the Jan 12 paper.

[Fatima0065]

LETS get this thread going:

Model of Benzene:
-around each carbon atom there is a triganal planar shape and a 120 bond angle
-there are sideway overlap of p-orbitals on the crabon atoms forming a pi cloud with electron denity above and below the plane containing six carbons. The pi electrons are delcoalised (spread ove rmore than 2 carbon atoms)..this causes elctron density to decrease and so there is not enough elctron density to polarise molecules for example bromine

Benzene undergoes substitution recation because an addition reaction would disrupt the delocalisation of the ring.

Cyclohexene: the pi bonds are concentrate dbtween two carbon atoms therefore electron density increases so it is able to ppolarise bromine more easily.

Phenol: is more reactive than benzene...
there is a lone pair of electrons on the oxygen atom in the delocalised pi system.
th OH group activates teh benzene ring therefore elctron density increases arond the ring so molecules are polarised more easily.
so electrophiles are attracted more easily....

feel free to add anything if you want

[otrivine]

(Original post by Fatima0065)
LETS get this thread going:

Model of Benzene:
-around each carbon atom there is a triganal planar shape and a 120 bond angle
-there are sideway overlap of p-orbitals on the crabon atoms forming a pi cloud with electron denity above and below the plane containing six carbons. The pi electrons are delcoalised (spread ove rmore than 2 carbon atoms)..this causes elctron density to decrease and so there is not enough elctron density to polarise molecules for example bromine

Benzene undergoes substitution recation because an addition reaction would disrupt the delocalisation of the ring.

Cyclohexene: the pi bonds are concentrate dbtween two carbon atoms therefore electron density increases so it is able to ppolarise bromine more easily.

Phenol: is more reactive than benzene...
there is a lone pair of electrons on the oxygen atom in the delocalised pi system.
th OH group activates teh benzene ring therefore elctron density increases arond the ring so molecules are polarised more easily.
so electrophiles are attracted more easily....

feel free to add anything if you want

shall we revise asking each other questions?

[Fatima0065]

Benzene undergoes electrophillic substitution eractions in the presence of a halogen carrier catalyst:

C6H6 +Br2---> C6H5BR + HBR

to react with a methyl group...an electrophile is formed first:

ALCl3 + ch3Cl -----> AlCL4 - + ch3+

[Fatima0065]

(Original post by otrivine)
shall we revise asking each other questions?

yep ill start