Benzene, is a cyclic hydrocarbon and contains only carbon and hydrogen only. It is a trigonal planar (molecule/structure) and bond angle around each carbon atom is 120. Benzene has 4 outer shells of electrons, three of these electrons are shared between a carbon atom and one of the hydrogen atom, this called sigma bond and is sited above and below the plane of the carbon (C-C) bond. The 4th outer shell of electron is the 2p orbital in which the p orbital overlaps and creates a region of high electron density. The benzene is delocalised as the electrons are shared between the 6 carbon atoms , through out the whole structure. Also, in benzene the c-c bond length is the same.

(edited 11 years ago)

Reply 446

otrivine

Anyone up for revision

Reply 447

TheFootyKing19

Original post by Zzzyax

describe structure and bonding in benzene [5]

- Pi bonds are formed by the overlap of adjacent p-orbitals above and below the ring
- Resulting pi bonds are delocalised and form an electron cloud above and below the ring
- There are 6 equal C-C bonds each intermediate in length between a single C-C and a C-C double bond. The bonds in benzene are all of same length
- Ring is planar
- Bond angle is 120 degrees

Reply 448

TheFootyKing19

Original post by otrivine

Anyone up for revision

Me! LETS ROLL ON!

Define chromatography (1)
How is separation acheived by solid stationary phase (1)
Give 2 limitations for TLC (2)
Give 2 limitations for GC (2)
How does GC-MS work (3)
Give the reagents and conditions to make an azo dye (5)
What are phenols used for (2)

Reply 449

otrivine

Original post by TheFootyKing19

sure, lets revise chapters 1 and 2 and Proton NMR!

Reply 450

otrivine

anyone up for revision :smile:

Reply 451

MasterYi

Original post by otrivine

anyone up for revision :smile:

Hello.

Reply 452

otrivine

Original post by MasterYi

Hello.

Hello,my friend! where were you , I felt so alone :frown:

Shall we start :biggrin:

Reply 453

MasterYi

Original post by i'm the daddy!

do you have legacy papers/mark schemes for unit F321 and F325 by any chance??
(Going to be tough June with three chem modules!!)

Why are you doing 3 Chem modules!?

I don't think I have any legacy stuff, but I do have a huge folder of items for F325. It has all papers up to date, a lot of resource papers and some good notes.

https://mega.co.nz/#F!IR1EkJYa!AWU6DT9zS5oTBymDeXpNcg

All of my F321 stuff which I collected in case I needed to resit it this June. INCLUDES ALL PAST PAPERS/RESOURCE PAPERS/ AND GOOD NOTES.

https://mega.co.nz/#F!YF1BhJ4I!RcjCO01_4Jlm07XEDNeiJw

Feel free to download. These are not my work, I found everything on the internet.

(edited 11 years ago)

Reply 454

MasterYi

Original post by otrivine

Hello,my friend! where were you , I felt so alone :frown:

Shall we start :biggrin:

At work. You first.

Reply 455

otrivine

Original post by MasterYi

At work. You first.

Oh, what do you work as ? :smile:

Define: chiral carbon (2)

Reply 456

MasterYi

Original post by otrivine

Oh, what do you work as ? :smile:

Define: chiral carbon (2)

Part time job as a Robot designer/creator/seller.

A carbon atom with 4 different groups attatched to it.

Reply 457

otrivine

Original post by MasterYi

Part time job as a Robot designer/creator/seller.

A carbon atom with 4 different groups attatched to it.

correct,

does this mean that you created me! :rolleyes:

Reply 458

MasterYi

Original post by otrivine

correct,

does this mean that you created me! :rolleyes:

Probably not; because all my robots are built to the highest standards.

Butanal and butanone both react with 1,2-DNP to produce mixtures with yellow/orange ppt.

Outline how the mixtures containing these yellow/orange ppts can be used to distinguish between butanal and butanone.

[3marks]

Reply 459

otrivine

Original post by MasterYi

what? Am I not the highest standard :frown:

Once, you added the 2,4 DNP solution derivative , forms orange/yellow ppt, the ppt is slightly impure and therefore is recrystallised in order for ppt to become slightly more pure. You filter as well. Then measure the melting point and compare with data base(book) values and then to to find out if the compound is either butanal or butanone.