OCR F324-June 2013 Chemistry

The amino acids produced are racemic mixture, this is because the (chiral centre) carbon atom is attached to 4 different atoms or groups of atom, and hence, can form 2 isomers which means , 2 non super imposable images of each other, one isomer rotates plane polarised light clockwise while the other isomer rotates plane polarised light anticlockwise, so results in these two isomers/mixture cancelling each other out.

Hi, can you confirm Zzzyax asked a question about protein hydrolysis , I pretty sure , I am not sure but when a protein is hydrlysed a carbon atom is attached to 4 different variables for optical isomerism to take place and can form mirror images?

The general formula of an alpha amino acid is RCH(NH2)COOH. If R is H (glycine) then there are two Hydrogens attached to the Carbon so it is not chiral. However in proteins (chain of amino acids joined by amide bonds) you have many different R groups, all of which (apart from glycine as I showed above) have at least one chiral carbon so will exist as a mixture of stereoisomers.

When you hydrolyze a protein you will pretty much always get a mixture of stereoisomers (unless it is completely made of glycine).

Whether or not it will be racemic I do not know. Will equal amounts of each left and right isomer of each stereoisomer be produced?

Thats what I was thinking, if I am not mistaken in an amino acid, the carbon is attached to carboxyl , amine and a variable R group and a single hydrogen atom, alanine has a chiral centre, if it chiral this means there are 4 different groups or atoms attached, so can it not form mirror images?

which one?

when the ethanoic anhydride reacts with an alcohol, how does the bond break to form the methyl ehtanoate

You dont need to know specifically how, however it breaks by gently heating it resulting with two ethanoic acid compounds and one of them reacts with methanol, the other ethanoic acid is just a product. This is why using anhydrides give better yield.

They come on a disc which comes with the book, I've lost my disc =/

so have i :/ could somebody send them ?

They come on a disc which comes with the book, I've lost my disc =/

Here you go. https://mega.co.nz/#!7c8iyJoS!Mqv1fnyInhRlrZgsZbe9aEixpeAvnrABIf3EiBDS3qM

are there any extra questions on the CD? I never got a cd :'(

It just has some tips and multiple choice questions; nothing special that will give you an advantage.

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Here you go. https://mega.co.nz/#!7c8iyJoS!Mqv1fnyInhRlrZgsZbe9aEixpeAvnrABIf3EiBDS3qM

that would get you the marks, it doesn't matter which ones are flipped, just an example of one of the possible structures in the mark scheme