Quick question: an amino acid at its isoelectric point has only 1 positive end and 1 negative end yeah? As in carboxyl groups on side chains (such as glutamic acid) are not effected as a zwitterion? If someone could clear this up for me I'd be grateful

Reply 1884

wl1

Original post by Raj Kang

Think of it like this, groups that have nh2 or oh attached are always going to have splitting pattern of singlet. This is because it has to be adjacent to proton on the next carbon atom

Great, thanks. So -NH and -OH protons will have singlet splitting patterns even if they are adjacent to a carbon with a proton?

Reply 1885

BeckyChatfield

Original post by Myocardium

I just did this paper!! In amino acids the NH2 Group can accept protons, i.e in an acidic solution and the COOH group donates protons i.e in a basic solution. A lower isolelectric point would indicate that the amino acids ability to accept protons has increased (so a more acidic solution contains more protons), the NH2 Group is the one that accepts protons so the isoelectric point is lowered!
Could be easier to think about is like if the isoelectric point is more acidic, then the amino acid must be more basic and vice versa!
Hope this helps!! :biggrin:

Reply 1886

Janjua

Hey, could someone tell me what rxns require heat under reflux? Thank you.

P.S you can just name the rxns I will get them :smile:

(edited 10 years ago)

Reply 1887

rukan

Original post by Myocardium

the zwitterion normally has a nh3+ and o- therefore when it is a much lower ph the o- goes to OH so now you have carboxylic acid therefore at a lower ph the cooh will be affected at a much higher ph value the nh3 goes to nh2 therefore it will be the nh2 functional group being affected at a much higher pH

Reply 1888

om-nom ._.

Original post by Jack9909

yeah you're right :smile:

it has to have a neutral charge at the isoelectric point so it must only have one negative end and one positive end. this confused me to, have a look at june 12 paper Q2 part c and the markscheme, that will clear it up for you :smile:

Reply 1889

om-nom ._.

do stereoisomers have the same structural formula? what is the definition??

Reply 1890

rukan

Original post by janjua

hey, could someone tell me what rxns require heat under reflux? Thank you.

P.s you can just name the rxns i will get them :smile:

1) halogeoalkane to alchol
2)alchol + acid to ester
3)notrobenzene to phnylamine
4)halogenoalkane to amine

THATS ALL I CAN REMEMBER

Reply 1891

Bazuka

Original post by om-nom ._.

do stereoisomers have the same structural formula? what is the definition??

Stereoisomers have the same structural formula but a different arrangement of the atoms in space.

Reply 1892

hopefulmedic28

Original post by om-nom ._.

do stereoisomers have the same structural formula? what is the definition??

Same structural formulae, different arrangement of atoms in space :smile:

Reply 1893

Meado123

Hey can someone please help me out on Q3 C on the June 2010 paper?

Paper: http://www.ocr.org.uk/Images/59707-question-paper-unit-f324-rings-polymers-and-analysis.pdf

Mark scheme: http://www.ocr.org.uk/Images/59704-mark-scheme-unit-f324-rings-polymers-and-analysis-june.pdf

Reply 1894

om-nom ._.

Original post by Bazuka

Stereoisomers have the same structural formula but a different arrangement of the atoms in space.

ok so they have the same molecular and structural formula?

Reply 1895

hopefulmedic28

Synthesising primary aliphatic amines I just cannot get my head around. If anyone has an explanation for dummies it would be much appreciated! :smile:

Reply 1896

estudiante_numero1

Sorry if this has already been posted here/enquired about, but does anyone have a digital copy of the January 2013 question paper and mark scheme please? :3

Any links etc would be much appreciated! :biggrin:

Posted from TSR Mobile

Reply 1897

rukan

Original post by estudiante_numero1

sorry if this has already been posted here/enquired about, but does anyone have a digital copy of the january 2013 question paper and mark scheme please? :3

any links etc would be much appreciated! :d

posted from tsr mobile

page 94 post 1877

Reply 1898

otrivine

quick question

http://www.ocr.org.uk/Images/65129-question-paper-unit-f324-rings-polymers-and-analysis.pdf

why is it only aspirin reacts with the Na2CO3 cause both compounds consist of carbonyl groups/?

Reply 1899

om-nom ._.

Original post by hopefulmedic28

Synthesising primary aliphatic amines I just cannot get my head around. If anyone has an explanation for dummies it would be much appreciated! :smile:

heat
halogenoalkane + excess ethanolic ammonia ----------> aliphatic amine + by-product

e.g. CH3CH2Br + NH3 ---------> CH3CH2NH2 + HCl

then HCl + NH3 -----> NH4+Br-

- it's nucleophilic substitution, the ammonia is acting as a nucelophile
- the ammonia has to be in excess to prevent further substitution of the aliphatic amine reacting with the halogenoalkane