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last SG · 2015-08-19T22:54:00+00:00

Topic : atomic radius Hi! This is from singapore cambridge nov a level exam year 2010,Paper 1 qn 1Qn: which element has the largest atomic radius?BrKKrScSo...

Flying grenade SG

2 methyl groups joined to one carbon or 1 ethyl group is more electron donating by induction?

should be 2 methyl groups.

what about 2 ethyl groups compared to 3 methyl groups?

UltimaOnline SG

https://www.dropbox.com/s/nu04p9d3tkvhbox/20161006_125259.jpg?dl=0 pg 194

what product will form when ester, amides, acyl halides react with 24dnph, Nu Sub to give what?

Draw out the mechanism then you'll know.

UltimaOnline SG

why is OH- hydroxyl group a better leaving group than carbanion R- or hydride H- ?

OH- is also a strong nucleophile like R- and H- right ?

cks say due to the above reason, aldehydes and ketone undergoes nu add, carboxylic acid undergo nu sub

Who lagi strong? Who lagi unstable?

UltimaOnline SG

https://www.dropbox.com/s/hld2siryk5xcyxt/20161006_135648.jpg?dl=0

how do we know which substituent group is dominant?

and in this case cks writes weakly activating CH3 groups dominate the strongly deactivating NO2 group ?

He's right.

UltimaOnline SG

e- from NO2 group can delocalise into b.ring of nitrobenzene too right?

https://www.dropbox.com/s/akatwjm0cr5ytdx/20161006_144236.jpg?dl=0

Draw the resonance contributors to substantiate your claim.

UltimaOnline SG

2 methyl groups joined to one carbon or 1 ethyl group is more electron donating by induction?

should be 2 methyl groups.

what about 2 ethyl groups compared to 3 methyl groups?

Irrelevant, because in such scenarios other factors (figure them out yourself, go ask your school teacher or private tutor, and don't reveal them on the forum, edart sterces) will outweigh inductive effects.

Flying grenade SG

Who lagi strong? Who lagi unstable?

why R- and H- more strong and unstable than OH- ?

Flying grenade SG

He's right.

Flying grenade SG

HAHAHAHA OK I GOT IT ALR

UltimaOnline SG

why R- and H- more strong and unstable than OH- ?

If you still can't figure out, go ask your school teacher or private tutor. Edart sterces.

UltimaOnline SG

Because he's not wrong.

If you still can't figure out, go ask your school teacher or private tutor. Edart sterces.

Flying grenade SG

trans

https://www.dropbox.com/s/oabzqc9aqa0y8qp/20161006_171942.jpg?dl=0

https://www.dropbox.com/s/2dxoa52rjsq0qz2/20161006_172012.jpg?dl=0

Flying grenade SG

eh 2 carboxylic acids undergo dehydration to form acid anhydride uh?

can i name this rxn condensation?

https://www.dropbox.com/s/52omev0kniqpmfz/20161006_175926.jpg?dl=0

Flying grenade SG

ooh just realised nitrobenzene cannot act as a base as N atom does not have a lp of e-

UltimaOnline SG

eh 2 carboxylic acids undergo dehydration to form acid anhydride uh?

can i name this rxn condensation?

https://www.dropbox.com/s/52omev0kniqpmfz/20161006_175926.jpg?dl=0

Obviously. Obviously.

UltimaOnline SG

ooh just realised nitrobenzene cannot act as a base as N atom does not have a lp of e-

Obviously.

Flying grenade SG

Because he's not wrong.

If you still can't figure out, go ask your school teacher or private tutor. Edart sterces.

circular reasoning

Flying grenade SG

Obviously. Obviously.

thanks

UltimaOnline SG

circular reasoning

Suitable for coconaden pple like u. U still stubbornly keep reading ur books and keep asking qns about them, instead of doing Prelim papers and asking qns from there instead, it'll be reflected in ur final A level results. For A grade students, the studying books stage is long over, the prelim paper practicing stage is now.

supercat SG

Hi, may I ask A Level 2012 P3 q5 c?

For this structure elucidation question,I derived that L has no aldehyde/ketone/alcohol/COOH groups.

M has to be an acidic salt, and alkene is present in M.

I have problems deducing M, assuming my L is right.

L is an acid anhydride right? But my L seems to be "cyclic" and I don't know how to add NH3 to it. From the question, it seems that the whole NH3 is added. How can NH3 be added when nothing is removed??

Some of my thinking: L is similar to acyl chloride, so reaction may be similar. But to form salt...?

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