Chemistry P4 Help needed

[bineetojha]

please help me with the benzene and NMR topics and hints for application portion !!!

 

[fluffycloud]

^I need help with Benzene Structure.
In reaction Kinectics-Rate Mechanisms,I don't understand that,could someone explain that too!
Cheers!

 

[bineetojha]

well i cold help u with the physical portion.. but not benzene //

 

[zeebujha]

well i cold help u with the physical portion.. but not benzene //

can you please explain why the color of halogen deepens down the group! The syllabus mentions n-(pi)* transition but I seriously am at loss to understand that!

 

[zeebujha]

please help me with the benzene and NMR topics and hints for application portion !!!

what kind of help do you require with benzene?

 

[zeena123]

Tell me why in May/June 2010/ 43, question 2.b.i they take the lattice energy as positive? It doesn't make any sense.

 

[bionology]

^I need help with Benzene Structure.
In reaction Kinectics-Rate Mechanisms,I don't understand that,could someone explain that too!
Cheers!

http://www.chemguide.co.uk/mechanisms/elsubmenu.html#

here ^, any further need, please specify

 

[zeena123]

Also, in the same paper (43/M/J/10) question 7.d.i doesn't make sense to me. How do we know what the chain is supposed to be?

 

[fluffycloud]

May june 2010 Paper 41 Q5 ( b i) How do you get that value???

 

[fluffycloud]

May juen 2010 paper 43 how do you the E naught values of PBO2 +AH +SO4 +2E---------PBSO4 +2H20

 

[zeena123]

May juen 2010 paper 43 how do you the E naught values of PBO2 +AH +SO4 +2E---------PBSO4 +2H20

You mean question 8.b? Find the E values from data booklet for PbO2 + 4H+ +2e ---> Pb2+ + 2H2O and the other reaction and then the more positive value minus the less positive will give you the E of cell.

 

[fluffycloud]

ohh damn! I was using the E values in textbook.
SHOOOT,forgot about data booklet.

 

[bionology]

which Q? i could'nt find any relating to ur question

 

[maniac33]

Also, in the same paper (43/M/J/10) question 7.d.i doesn't make sense to me. How do we know what the chain is supposed to be?

.....in this thing we've gotta make the sequence of amino acid in such a way that it can form all the given tripeptides in the questn.....so since it shud start from lysine...so lets start from lys-val -ser now there's another tripeptide ser-ala-gly....so u get -ser- common.....now merge the chains.....lys-val-ser-ala-gly-.....(now if u did notice u've already included the tripeptide -val-ser-ala- in your newly formed sequence.....)again merge this chain with -gly-ala-gly-.....with -gly- common .you get...-lys-val-ser-ala-gly-ala-gly-....and now the only left tripeptide is -ala-gly-asp-......since u already have the last amino acid sequenced as ala-gly so now just put _asp_after gly......so ur shortest polypeptide thus required is lys-val-ser-ala-gly-ala-gly-asp.........hope u got it!

 

[zeena123]

And how is it that the answer to the last part of this question is Aspartic acid/ lysin.

 

[bineetojha]

@zeena halogens ..means group 7 it's in as..and their color deepen because of increasing vandewaal's forcea due to increasing molecular size down the group.//

 

[zeebujha]

@zeena halogens ..means group 7 it's in as..and their color deepen because of increasing vandewaal's forcea due to increasing molecular size down the group.//

first it was me who asked the question (confusion between zeena and zeebu). I don't think intermolecular forces account for the deepening of the color

 

[zeena123]

It is due to increasing Van der Waals' forces.

 

[maniac33]

And how is it that the answer to the last part of this question is Aspartic acid/ lysin.

aspartic acid has two -cooh groups....and lysine has two -Nh2 group...so this makes the amino acids slightly acidic or basic.....

 

[zeena123]

I see now. Thank you