Edexcel AS Chemistry: 4th June 08

Yeah, i mentioned in my previous post that i did think of it as it should give that compound but since i have never come across it i thought it'd be better for me to just stick to what i've learned. Besides, the reaction could be incomplete and give rise to bromoethane too. Anyway, i won't bump my head into the wall just for one mark. I've learned a new compound called ethyne so i should be rejoicing.

Reply 262

fait

OP

I'm pretty sure they will take other possibilites into account because of the fact we didn't learn anything like that anyway. Same for that question regarding the -diol, we only learn about what happens to 1 alcholol group, not two in a compound, so all is good hopefully.

Reply 263

ismail jamaluddin

~Adel~

Yeah, i mentioned in my previous post that i did think of it as it should give that compound but since i have never come across it i thought it'd be better for me to just stick to what i've learned. Besides, the reaction could be incomplete and give rise to bromoethane too. Anyway, i won't bump my head into the wall just for one mark. I've learned a new compound called ethyne so i should be rejoicing.

lol you should rejoice cause wasnt that hard

Reply 264

fait

I'm pretty sure they will take other possibilites into account because of the fact we didn't learn anything like that anyway. Same for that question regarding the -diol, we only learn about what happens to 1 alcholol group, not two in a compound, so all is good hopefully.

Examiners are on our side apparently :tongue:

Reply 265

fait

OP

Oxy

Examiners are on our side apparently :tongue:

Here's to wishful thinking! :biggrin:

Reply 266

ismail jamaluddin

lol you should rejoice cause wasnt that hard

True..or else i'd have grieved over that one mark. It was really quite easy compared to my first sitting.

Reply 267

Medicine Man

16

so it was ethyne and not ethene?
wtf?

Reply 268

Theoretically it should be ethyne but we are not expected to know the name i suppose. There might be a few answers for that question. Anyway, it's just a one mark question so there's no need to over-react on it..lol..

Reply 269

i would still liek to hear the theory about how it becomes ethyne if he knows it all?..This shall be interesting

Reply 270

It's quite logical to be honest, oxy. That structure went through my mind but i didn't write it because i never learned it before. Elimination process will get rid of HBr(per functional group), since there were two functional groups, 2 molecules of HBr will be eliminated and i think that gives ''ethyne''.

Reply 271

ismail jamaluddin

Oxy

i would still liek to hear the theory about how it becomes ethyne if he knows it all?..This shall be interesting

we know the reaction of 1bromoethane with KOH(ALC)
eliminates one H and Br thus giving Ethene C2H4
so in the reaction of 1,2bromoethane with KOH(ALC)
two Br and two h removed thus giving C2H2
that is why they also gave you the option to write the formula or name of the compound
even if you did not know the name of the compound you could have wrote the formula one other possible answer might be 1BROMOEHTHENE this is possible if you assume only one halide ion reacts

Reply 272

eug.galeotti

I think the same would apply to oxidising a diol. If you know how to oxidise a primary and secondary alcohol, just apply the same principals to those OH groups on both ends.

Reply 273

Edexcel's chemistry unit 5 paper now looks like a blessing to me after siting for so many other A2 papers..i'm officially hating edexcel now.

Reply 274

ismail jamaluddin

we know the reaction of 1bromoethane with KOH(ALC)
eliminates one H and Br thus giving Ethene C2H4
so in the reaction of 1,2bromoethane with KOH(ALC)
two Br and two h removed thus giving C2H2
that is why they also gave you the option to write the formula or name of the compound
even if you did not know the name of the compound you could have wrote the formula one other possible answer might be 1BROMOEHTHENE this is possible if you assume only one halide ion reacts

Why can it not just take Br2 instead of 2 lots of HBR? because if u react an alkene with Br2 u get 1,2 dibromo ..and if what ur saying is true it knocks of a total of 4 atoms? If you could get some proof please?

Reply 275

oxy, ismail is probably right. It was a reaction with KOH(ethanolic) so that means it had to be an elimination reaction, so one H and one Br will be detached from the reactant organic compound.

Reply 276

faire enough if u think so but i dont. I know its elimination - what you've just wrote saying 1 Br and H will be detatched isn't what ismail is saying, he said noth bromine and 2 hydrogen atoms are removed leaving C2H2? Why not just take both bromine atoms, surely taking 2 bromine atoms is easier than two bromine atoms plus 2 hydrogen

Reply 277

Medicine Man

16

yeah and isn't the C-Br bond longer and weaker so easily broken? Whereas the C-H bond will be stronger. Therefore i think 2 Br will be removed. But oh well, just a mark!

Reply 278