Lurkers, register with SgForums and ask ur H2 Chem qns here!
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page 309 , btm of page
is there any special name for R+ ion ?
alkylium ion? haha
there is such thing as alkylium ion
https://en.m.wikipedia.org/wiki/Carbenium_ion
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cool name lmao
https://en.m.wikipedia.org/wiki/Magic_acid
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Originally posted by Flying grenade:
page 309 , btm of page
is there any special name for R+ ion ?
alkylium ion? haha
Carbocation. When the C atom is part of the acyl group, then it's called the acylium ion (because the unipositive formal charge isn't stuck on C, it's delocalized by resonance over both the C and O atoms, try drawing both resonance contributors and thus the resonance hybrid). -
Originally posted by Flying grenade:
cool name lmao
https://en.m.wikipedia.org/wiki/Magic_acid
Don't just see something unusual only, then just copy and paste the link with a "cool name lmao". Learn whatever you can from it.For instance, try drawing out the full curved-arrow electron-flow mechanism (for both forward and backward reactions) using full displayed structural formula for the following equilibria.
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U.O. SUPER ZAI !!!!!
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pge 317 cstoh advanced guide
when conc alkaline kmno4 is heated under reflux with the organic product, brown MnO2 is formed. will this happen if Acidified kmno4 is used instead?
page 311
white ppt of benzoic acid is formed
so we can see both white ppt and brown ppt?
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page 318 common errors section
1st statement : should be halogenation of *alkenes*, not halogenation of *alkanes*, use Br2(l) in CCl4, dark
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page 318
arrow from pi bond of alkene reaches H atom
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Originally posted by Flying grenade:
pge 317 cstoh advanced guide
when conc alkaline kmno4 is heated under reflux with the organic product, brown MnO2 is formed. will this happen if Acidified kmno4 is used instead?
page 311
white ppt of benzoic acid is formed
so we can see both white ppt and brown ppt?
What do u think? And yes. -
Originally posted by Flying grenade:
page 318 common errors section
1st statement : should be halogenation of *alkenes*, not halogenation of *alkanes*, use Br2(l) in CCl4, dark
Yes. -
Originally posted by Flying grenade:
page 318
arrow from pi bond of alkene reaches H atom
Yes. -
Eh Flying Grenade, go do your Prelim papers lah. Don't delude yourself into thinking that just coz you keep OCD asking trivial qns on every single CS Toh page, means you're working hard to prepare yourself to get A grade for A levels.
Start spamming 2015 and 2014 Prelim papers instead, and make it such that 90% of questions you ask from now on in SgForums, are regarding Prelim paper questions. And also, before asking any questions from the Prelim papers, make sure you go through the Mark Scheme answers first. Then ask.
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page 342 Cstoh advanced guide
mechanism for part 3a)
the 'slow' and 'fast' need to cancel out right?
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Originally posted by Flying grenade:
page 342 Cstoh advanced guide
mechanism for part 3a)
the 'slow' and 'fast' need to cancel out right?
Correct, there's no 'slow' or 'fast' step in SN2. -
for dot and cross diagrams, no need write Legend right, lol
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Originally posted by Flying grenade:
for dot and cross diagrams, no need write Legend right, lol
No lah. But anion should use hollow dot (in addition to dot and cross), which you can give a legend to say it's from the cation.Eh Flying Grenade, go do your Prelim papers lah. Don't delude yourself into thinking that just coz you keep OCD asking trivial qns on every single CS Toh page, means you're working hard to prepare yourself to get A grade for A levels.
Start spamming 2015 and 2014 Prelim papers instead, and make it such that 90% of questions you ask from now on in SgForums, are regarding Prelim paper questions. And also, before asking any questions from the Prelim papers, make sure you go through the Mark Scheme answers first. Then ask.
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just realised George chong doesn't have a book for Physical Chemistry
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Originally posted by Flying grenade:
just realised George chong doesn't have a book for Physical Chemistry
Eh don't worry about George Chong, you do your Prelim papers lah! Every other JC student is practicing hundreds of Prelim papers now. You wanna lose out to them? -
Ultima can tell me what is E1 and E2 mechanisms??
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yes, im doing the papers
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Originally posted by Flying grenade:
Ultima can tell me what is E1 and E2 mechanisms??
Google be thy Sword, Wikipedia be thy Shield. -
page 279 cs toh advanced guide, bottom of page
should the curved arrow from lone pair of e- of N atom on nucleophile reach the carbon with delta +ve?
should curved arrow from within benzene ring reach the N atom of NO2+ electrophile?
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Originally posted by Flying grenade:
page 279 cs toh advanced guide, bottom of page
should the curved arrow from lone pair of N on nucleophile reach the carbon with delta +ve?
should curved arrow from within benzene ring reach the N atom of NO2+ electrophile?
Yes lah, will u stop it with these common sense mechanism qns??? Just cross reference with George Chong and Chan Kim Seng lah! And by now (3 months to A levels liao), the way to draw mechanisms should be common sense liao. Stop asking these silly and annoying qns. This is almost the 10th silly qn u've been asking on mechanisms liao. Sheeesh. -
Hi. New poster. Here couldn't create a new thread so I have to ask here. So I've decided to retake my A levels this year and I am only starting to study for it now due to certain circumstances. I know it is quite late to study for it now but I really want to give it a shot. Not expecting stellar results, just want to get grades good enough to enter an engineering course in NTU or NUS. Preferably NUS due to personal reasons but I'm fine with NTU as well. (Government calling for more students to pursue engineering isn't very comforting for me because I'm scared that demand for the courses will go up and the competition would be stiff for the limited slots.)
Currently I am starting on chemistry first because I have some notes on it. I don't remember much so I thought starting with topical would be better. Doing a topical TYS which I have from my jc days. Feel that the answers are abit lackluster. Not sure whether I should continue using it to study up each of the topics. Can't provide a picture now. I know that ultimaonline recommend CS Toh books. Wonder if it is suitable for someone like me who is starting from close to zero.
I'm taking PCME as my subject combination and I will be taking paper 5 for the sciences.
As for other subjects, I'm not sure how to study for it. I'm just using a topical TYS for physics which I think has detailed explanation. Don't know how to start for math, econ and gp. I need some advice as well as recommendation for which books I should get to study for A levels. It's hard to explain my situation in detail. Hope that someone could give me some guidance. Thanks.
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Originally posted by senga:
Hi. New poster. Here couldn't create a new thread so I have to ask here. So I've decided to retake my A levels this year and I am only starting to study for it now due to certain circumstances. I know it is quite late to study for it now but I really want to give it a shot. Not expecting stellar results, just want to get grades good enough to enter an engineering course in NTU or NUS. Preferably NUS due to personal reasons but I'm fine with NTU as well. (Government calling for more students to pursue engineering isn't very comforting for me because I'm scared that demand for the courses will go up and the competition would be stiff for the limited slots.)
Currently I am starting on chemistry first because I have some notes on it. I don't remember much so I thought starting with topical would be better. Doing a topical TYS which I have from my jc days. Feel that the answers are abit lackluster. Not sure whether I should continue using it to study up each of the topics. Can't provide a picture now. I know that ultimaonline recommend CS Toh books. Wonder if it is suitable for someone like me who is starting from close to zero.
I'm taking PCME as my subject combination and I will be taking paper 5 for the sciences.
As for other subjects, I'm not sure how to study for it. I'm just using a topical TYS for physics which I think has detailed explanation. Don't know how to start for math, econ and gp. I need some advice as well as recommendation for which books I should get to study for A levels. It's hard to explain my situation in detail. Hope that someone could give me some guidance. Thanks.
Yup, just use CS Toh's Study Guide and memorize the entire book.And buy at least 2 different H2 Chem TYS available from Popular, coz different TYS give different answers (since Cambridge has a legal agreement with Sg Govt to keep the actual Sg A level mark schemes a secret), so you should cross reference across both answer booklets. If for questions that give totally different answers (and there will be many), and if you're not sure which answer is better or more correct, post about it here, and I'll advise you.
Don't bother doing Prelim papers, coz at this late stage when you've not yet started preparing for H2 Chem, doing Prelim papers will only demoralize you and be counterproductive. Better to focus on doing only Sg TYS papers.