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Infrared spectroscopey help

I don't understand this question at all. :frown:

Could someone please talk me through it? I would really appreciate it! All I know is that the broad peak around 3400c/m is an -OH group. :colondollar:

I can't do anything else? Pleasee help! Thanks :smile:

Reply 1

username913907

Original post by Mr Tall

I don't understand this question at all. :frown:

Could someone please talk me through it? I would really appreciate it! All I know is that the broad peak around 3400c/m is an -OH group. :colondollar:

I can't do anything else? Pleasee help! Thanks :smile:

Well good start.... what functional group is this OH then?

Reply 2

Ari Ben Canaan

Original post by Mr Tall

I don't understand this question at all. :frown:

Could someone please talk me through it? I would really appreciate it! All I know is that the broad peak around 3400c/m is an -OH group. :colondollar:

I can't do anything else? Pleasee help! Thanks :smile:

Good, you've identified an alcohol group. What do you know about oxidising alcohol groups ?

Reply 3

Mr Tall

Original post by Ari Ben Canaan

Good, you've identified an alcohol group. What do you know about oxidising alcohol groups ?

You get an aldehyde?

Reply 4

Ari Ben Canaan

Original post by Mr Tall

You get an aldehyde?

That's a good suggestion, but what else could you get ?

EDIT : Depending on the conditions you may not stop at producing an aldehyde i.e. the reaction may produce something else.

Reply 5

Mr Tall

Original post by Ari Ben Canaan

That's a good suggestion, but what else could you get ?

A carboxylic acid?

Reply 6

Ari Ben Canaan

Original post by Mr Tall

A carboxylic acid?

That's good, but these products originate from what kind of alcohol group ? What other class(es) of alcohol group(s) could you have begun with ?

Reply 7

Ari Ben Canaan

I'll have to leave in a bit so I'll help you out a bit more.

So we know we're starting off with an alcohol group. You should know that there are 3 classes of alcohols... Primary, Secondary and Tertiary.

Tertiary alcohols cannot be oxidised.

Primary and secondary alcohols produce different products from each other. Consider these final products along with their molecular formulas and you should be good to go :smile:

Reply 8

andrewruss

A Primary Alcohol produces an Aldehyde once oxidised and if that aldehyde is further oxidised, it creates a carboxylic acid;
A Secondary Alcohol produces a Ketone;
A Tertiary Alcohol cannot be oxidised.

Out of curiosity, is this AS or A2 Chemistry?

Reply 9

Ilhajxichjabv

X is a primary alcohol. Reacting it with an excess of acidified potassium dichromate produces a carboxylic acid, which is what Y is. The broad peak signifies the hydroxyl group and the large peak next to it as the -C-H bond.

Reply 10

AdamskiUK

Original post by andrewruss

At a guess, this is A2 Chemistry within the AQA spec. You do some infra red questions at AS, but rarely as complex as this. The fact that it's thrown in the oxidising of an alcohol group indicates that it's a pretty synoptic A2 question.

From my experience of doing PPQs, anyway!

Reply 11

andrewruss

Original post by AdamskiUK

Ahhh, I am only an AS Student doing the Edexcel exam board! It explains a lot otherwise I'd have to start revising more thoroughly. :P

Reply 12

AdamskiUK

Original post by andrewruss

Ahhh, I am only an AS Student doing the Edexcel exam board! It explains a lot otherwise I'd have to start revising more thoroughly. :P

Well AQA AS does include the oxidation of both primary and secondary alcohol groups to aldehydes/carboxylic acids and ketones respectively.

Their favourite A2 IR spec questions are like this.