HELP! MASS SPEC PROBLEM

[methodsboy]

hey
i've got a chem SAC tommorrow and i dnt know how to do this question 
could someone please help - Question 12 and 13

[IMG]http://img12.imageshack.us/img12/2094/massspectometry.jpg[/img]

Thanks

[TrueTears]

is question 12 a) i

if it is, then I shall continue, if not, then my method must be wrong.

[methodsboy]

umm no, its : CH3COOH+

[TrueTears]

lol owned. Got no idea frankly. There's not enough info to deduce what compound it is. Is the parent molecular ion given?

[d0minicz]

the fact that it turns methyl orange pink suggests carboxylic acid
and the highest m/e is 60
so i guess you play around ensuring that you have a COOH and the carbons and hydogens are proportional etc :S
then work your way from there
sorry if isnt any help lols :S

[TrueTears]

but how do you know methyl orange suggests carboxylic acid? I know when methyl orange indicator turns pink/red it means its an acid, but why carboxylic specifically?

[d0minicz]

i couldnt deduce anything else cuz im shit lol

[Mao]

Q11)

For Mass Spec, IR and NMR in VCE, you assume it is an organic molecule,

Parent peak (heaviest and abundant) - 60
Base peak (most abundant) - 43
Second most abundant peak - 45

From 60 to 43, a fragment of weight of 17 has been lost, this is -OH
From 60 to 45, a fragment of 15 has been lost, this is CH3
It is an acid, most likely carboxylic acid.

Checking Mr of CH3COOH, bingo.

Ethanoic acid, peak at 60 is CH3COOH+, peak at 45 is COOH+, peak at 43 is CH3C(=O)+, peak at 15 is CH3+

[TrueTears]

Q11)

For Mass Spec, IR and NMR in VCE, you assume it is an organic molecule,

Parent peak (heaviest and abundant) - 60
Base peak (most abundant) - 43
Second most abundant peak - 45

From 60 to 43, a fragment of weight of 17 has been lost, this is -OH
From 60 to 45, a fragment of 15 has been lost, this is CH3
It is an acid, most likely carboxylic acid.

Checking Mr of CH3COOH, bingo.

Ethanoic acid, peak at 60 is CH3COOH+, peak at 45 is COOH+, peak at 43 is CH3C(=O)+, peak at 15 is CH3+

oh i see, gotta note that from now on.

[Mao]

13)

There are two carbon environments. Since there are three carbons in the molecule (propanol), it must be symmetrical about the central carbon (otherwise there will be three carbon enviroments).

Hence the molecule must be 2-propanol.

Remembering that atoms closer to electronegative atoms have higher chemical shifts:

on the carbon graph, the small peak on the left is the central carbon connected to the hydroxyl group, the tall peak on the right is the two outer carbons
on the proton graph, the sextuplet on the left is the single H connected to the central carbon (there are 6 H in its neighbourhood), the singlet is the H in OH (shielded by the O), and the doublets account for the 6 hydrogens on the outer carbons, as both of the CH3 group's neighbour is the H on the central carbon

[methodsboy]

13)

There are two carbon environments. Since there are three carbons in the molecule (propanol), it must be symmetrical about the central carbon (otherwise there will be three carbon enviroments).

Hence the molecule must be 2-propanol.

Remembering that atoms closer to electronegative atoms have higher chemical shifts:

on the carbon graph, the small peak on the left is the central carbon connected to the hydroxyl group, the tall peak on the right is the two outer carbons
on the proton graph, the sextuplet on the left is the single H connected to the central carbon (there are 6 H in its neighbourhood), the singlet is the H in OH (shielded by the O), and the doublets account for the 6 hydrogens on the outer carbons, as both of the CH3 group's neighbour is the H on the central carbon

You Rock!