IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => IGCSE/ GCSE => Sciences => Topic started by: holtadit on November 06, 2009, 11:00:50 am

Title: Lactic acid
Post by: holtadit on November 06, 2009, 11:00:50 am: Look at question B9)D)ii

What is the displayed structural formula ??

you will find bothe the question paper and markscheme attached
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 06, 2009, 11:10:21 am: this is what the product will look like
here the C2H5OH will replace Hydrogen from the third carbon...
The H removed will react with the OH from ethanol to form water and this new compound will be formed
Title: Re: Lactic acid
Post by: holtadit on November 06, 2009, 11:20:04 am: Could u give me the displayed structural formula too - for my reference
Title: Re: Lactic acid
Post by: nid404 on November 06, 2009, 11:20:44 am: basically for any esterification....remember water is lost. Oh from ethanol is used....and one H from the acid is used to form water......

Put the rest of the structure as it is.....acid followed by alcohol......but while naming remember u name the alkyl(formed from alcohol) first and then the acid+oate

I'm dead tired...so im bound to say crap in this state....if u spot summin wrong lemme know.....
Title: Re: Lactic acid
Post by: nid404 on November 06, 2009, 11:22:20 am: Quote from: Ari Ben Canaan on November 06, 2009, 11:20:04 am
Could u give me the displayed structural formula too - for my reference

wait u want the structural formula or the displayed formula....2 different things actually.......what he's uploaded is a partially displayed formula i would say
Title: Re: Lactic acid
Post by: nid404 on November 06, 2009, 11:27:40 am: lactic acid structural formula is CH₃CHOHCOOH
ethanol is CH³CH₂OH

so structural formula of ethyl lactate would be...CH₃CHOHCOOCH₂CH₃
Title: Re: Lactic acid
Post by: nid404 on November 06, 2009, 11:32:55 am: Quote from: @d!_†oX!© on November 06, 2009, 11:31:55 am
perhaps this is wat u wanted

this is displayed formula

the one I gave above is structural....so uve got both now
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 06, 2009, 11:34:50 am: i already gave the structural formula nid...bt still thanks... ;D
Title: Re: Lactic acid
Post by: holtadit on November 06, 2009, 11:35:47 am: Thanks ppl understood everything now !!
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 06, 2009, 11:36:46 am: yr welcome ari....
keepp posting question like these....really interested in chem nd like solving especially ur question... :)
Title: Re: Lactic acid
Post by: nid404 on November 06, 2009, 11:38:42 am: Quote from: @d!_†oX!© on November 06, 2009, 11:34:50 am
i already gave the structural formula nid...bt still thanks... ;D

we ll the one u gave is actually not structural....structural formula shows the arrangement like specifically.....so u can't give the diagrammatic representation......and even if u write it like this with the bonds....u will have to show each bond separately like.....u can't put the last part as C₂H₅.....it has to be CH₂CH₃....very specific
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 06, 2009, 03:55:10 pm: Quote from: nid404 on November 06, 2009, 11:20:44 am
basically for any esterification....remember water is lost. Oh from ethanol is used....and one H from the acid is used to form water......

Put the rest of the structure as it is.....acid followed by alcohol......but while naming remember u name the alkyl(formed from alcohol) first and then the acid+oate

I'm dead tired...so im bound to say crap in this state....if u spot summin wrong lemme know.....

OH from the acid (lactic) is used, not ehanol. (alchol)
Title: Re: Lactic acid
Post by: nid404 on November 06, 2009, 04:16:14 pm: I think I'm write abt this......OH from ethanol used....and H from acid.....

hence the formula of ester still has a double oxygen with the acid......this can be further confirmed as the ester is alkyl( which confirms there is no OH) + acid...+ate
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 05:33:10 am: i'm still sure its from the acid. i checked my book too.
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 07, 2009, 06:00:09 am: aadi ur wrong !!! :(
i agree wid nid...its OH from alchohol nd H from acid...
see u remember an acid is an H⁺ donor not OH
u get it?????
nd if u dont get it still pllsss show me wid a diagram how an OH ion is coming from an acid....dts sooo weird.... ??? :P :o
Title: Re: Lactic acid
Post by: nid404 on November 07, 2009, 06:02:20 am: Quote from: A@di on November 07, 2009, 05:33:10 am
i'm still sure its from the acid. i checked my book too.

which book do u use?? I'm too sure abt this..since alcohol becomes alkyl.....it can't have a O single handedly....no not possible
Title: Re: Lactic acid
Post by: nid404 on November 07, 2009, 06:13:24 am: image doesn't open
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 07, 2009, 06:13:48 am: dude either i am not able to interpret it or it is actually some fault...plsss check nd let me know
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 06:13:59 am: check the diagram - http://filesmelt.com/downloader/ester.bmp
@nid - roger norris, roger stanbridge

maybe u guyz are confusing this reaction with a neutralization reaction, in that, the H from the acid is taken.

Na+(aq)+OH-1(aq)+H+(aq)+Cl-(aq) --> Na+(aq)+Cl-(aq)+H2O
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 07, 2009, 06:19:56 am: dude...the reaction is perfect but as u have chosen H from the ethanol and OH from the acid...its wrong...it has to be te other way round...
as in H from the acid....nd OH from ethanol..
thee is no doubt about onfusing wid neutralisation reaction....bt gotta understand dt be it neutralisation reaction or some other...an acid cannot give an OH^-ion...
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:20:47 am: it gives!!
i ahve also cheked my book!!
lactic acid gives OH!!
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 06:21:47 am: Quote from: @d!_†oX!© on November 07, 2009, 06:19:56 am
dude...the reaction is perfect but as u have chosen H from the ethanol and OH from the acid...its wrong...it has to be te other way round...
as in H from the acid....nd OH from ethanol..
thee is no doubt about onfusing wid neutralisation reaction....bt gotta understand dt be it neutralisation reaction or some other...an acid cannot give an OH^-ion...

u repeating the same point a thousand times dude. u want me to scan that page and send it over?
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:24:31 am: do it!!
let them see it!!
i am laso confused after reading manyimtes acid is H+ donor but here it does not follow it!!
i guess!!
Title: Re: Lactic acid
Post by: nid404 on November 07, 2009, 06:29:52 am: Ok.....I just revised some organic chemistry...and adi is right...it's the acid that give OH and alcohol that gives H

http://www.chemguide.co.uk/physical/catalysis/esterify.html

It's pretty complicated actually.......I haven't really started with organic chem in A level.....so to explain would be a problem........the mechanism explained in the site is pretty good....check it out

And for now evn if you don't get it....jst remember OH is from acid And H from alcohol
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:30:58 am: see!!
aadi and i were right!!!

yippie!!!
Title: Re: Lactic acid
Post by: nid404 on November 07, 2009, 06:32:11 am: Quote from: ~~~~shreycool~~~~ on November 07, 2009, 06:30:58 am
see!!
aadi and i were right!!!

yippie!!!

and the reaction is not as simple as adi has shown......that diagram has a lot of steps involved......
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:33:42 am: i guess organic chem is very tough!!
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 06:34:20 am: ahhh....finally!...

@adi - i know, u may pop-up again with ur arguements abt "H+ and donor" jk.. :P

check this - http://filesmelt.com/downloader/as.JPG

@nid - i have learnt wat my book says, for IGCSE ; the complicated stuff ur talking abt is probably not dere for IGCSE...
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:35:15 am: lets seee!!
hope this doesnt continue!!
stop the argument!!
now it is doen!!
OH from acid and H from alchohol!!
Title: Re: Lactic acid
Post by: nid404 on November 07, 2009, 06:36:32 am: Yes for IG students that's that.....OH from acid and H from alcohol......I might be able to explain once I'm done with mechanism of ester formation in A level...so now don't ask abt the donor stuff...pretty complex...cause there is a catalyst involved
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:37:12 am: great!!
at last the question is solved and adi is not popuing again as adi said!! :P
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 06:37:27 am: Quote from: nid404 on November 07, 2009, 06:36:32 am
Yes for IG students that's that.....OH from acid and H from alcohol......I might be able to explain once I'm done with mechanism of ester formation in A level...so now don't ask abt the donor stuff...pretty complex...cause there is a catalyst involved

sulfuric acid?
Title: Re: Lactic acid
Post by: nid404 on November 07, 2009, 06:37:48 am: yup dude
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 07, 2009, 06:38:28 am: okk.....Thanks aadi nd nid for explaining that to me.....i really thought it wud be as i said cuz dts exactly wt our teacher taught us....
so its gud that i know abt it now....
nd no aadi wont come up wid dt again....
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:39:21 am: wat sulfuric acid are you both talking abt??
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 06:39:52 am: Quote from: @d!_†oX!© on November 07, 2009, 06:38:28 am
okk.....Thanks aadi nd nid for explaining that to me.....i really thought it wud be as i said cuz dts exactly wt our teacher taught us....
so its gud that i know abt it now....
nd no aadi wont come up wid dt again....

its k , go tell that to ur world-class chemistry teacher (i remember u saying that to me) :P :P

@shrey - book khol be, H2SO4 is the catalyst
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:41:35 am: is ester formation rite??
then its k!!
cause i did not reeach till ester!!
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 07, 2009, 06:42:12 am: ya she still stays the world class teacher aadi.....perhaps there has been some problem...will get back to u soon....
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:45:56 am: best apne ghar ki hogi!! :P :P
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 06:47:54 am: Quote from: ~~~~shreycool~~~~ on November 07, 2009, 06:45:56 am
best apne ghar ki hogi!! :P :P
didnt get u??
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:49:14 am: apne he says that she still remains best!!
mein bola apne ghar ki hogi!!

i still like anjana ma'am!!

kya padhati thi be voh!!
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 06:50:11 am: Quote from: ~~~~shreycool~~~~ on November 07, 2009, 06:49:14 am
apne he says that she still remains best!!
mein bola apne ghar ki hogi!!

kya ghar ki hogi??

chhod, EADA...not here..plz
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:51:35 am: best hogi apne gahr mein hi!!
not in th world!!
samjha!!
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 07, 2009, 06:54:19 am: guys i just checked my own notebook...nd it has the same thing which ur book shows aadi....
i got confused...bt i wont tell u how i got confused cuz its a very funny thing...nd i cant stop laughing at wat a lame thing i was doing....
anyways...gud dt i gt confused...so i was corrected there and then by my gud friends on sf....Thanks guys...now i wud never forget it....

n shrey!!!!
dude u gotta respect her...because she's probably one of the very few teachers who i truly respect!!
Title: Re: Lactic acid
Post by: nid404 on November 07, 2009, 06:56:40 am: Quote from: ~~~~shreycool~~~~ on November 07, 2009, 06:51:35 am
best hogi apne gahr mein hi!!
not in th world!!
samjha!!

warning chahiye kya??

respect se baat kar
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:57:11 am: i respect many but there re some whom i respect alot!!
nd for sure she is not one of them!!! :P :P(joke)
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 06:58:45 am: guyz guyz, plz stop, not here plz, continue in EADA
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 06:59:42 am: the above debate to be continued in EADA thread!!!
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DA END!!
Title: Re: Lactic acid
Post by: @d!_†oX!© on November 07, 2009, 06:59:56 am: mr. shrey is continuing EADA here!!
Title: Re: Lactic acid
Post by: Ghost Of Highbury on November 07, 2009, 07:00:40 am: Quote from: @d!_†oX!© on November 07, 2009, 06:59:56 am
mr. shrey is continuing EADA here!!

didnt he just stop?
Title: Re: Lactic acid
Post by: nid404 on November 07, 2009, 07:01:16 am: STOP. No one posts now.
Title: Re: Lactic acid
Post by: ~~~~shreyapril~~~~ on November 07, 2009, 07:01:41 am: https://studentforums.biz/index.php/topic,4605.0.html
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