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Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: sharbeldam on September 04, 2020, 04:31:38 AM

Title: Ketamine MS
Post by: sharbeldam on September 04, 2020, 04:31:38 AM

If i'm given 3 base peak (M,M+1,M+2,M+3) of the compound ketamine and i have the abundance AND m/e for

M (100 relative abundance , 237 m/e)
M+1 (14.3 relative abundance , 238 m/e)
M+2 (33.3 relative abundance, 239 m/e)

but i'm only given the m/e (240) of M+3 and im required to find the abundance of M+3.

what is the way to do it?
I know that the M+2 should be from chlorine atom since 1:3 relative abundance from M. but how can i figure out and predict the abundance of M+3, i tried using percentanges and molecular formula but its not working out.
Is it right to do this...

Title: Re: Ketamine MS
Post by: AWK on September 04, 2020, 06:14:52 AM

Can you calculate the expected intensity for peak 274 from the compound composition?
Do the same for peak 276 using peak 275.

Title: Re: Ketamine MS
Post by: sharbeldam on September 04, 2020, 06:22:42 AM

Is it too much to ask for the calculation? I'm not really sure how to calculate (I edited the original post)

Title: Re: Ketamine MS
Post by: AWK on September 04, 2020, 06:27:55 AM

Peak 238 (M + 1) depends primarily on the number of carbon atoms in peak 237 (M).
The same relationship occurs between peaks 239 (M + 2) and 240 (M + 3).

Title: Re: Ketamine MS
Post by: sharbeldam on September 04, 2020, 06:36:17 AM

number of carbons = (abundance of M+1 ion/abundance of M ion) * (100/1.1)

t ketamine has 13 carbons, hence... solving for that, except putting M+3/M+2, in that equation?

Title: Re: Ketamine MS
Post by: AWK on September 04, 2020, 06:40:59 AM

If M shows intensity 100 then M+1  ==> 13·1.1

Title: Re: Ketamine MS
Post by: sharbeldam on September 04, 2020, 06:44:29 AM

yes but i need M+3,
so can i do

x/33.3*(100/1.1) = 13

Title: Re: Ketamine MS
Post by: AWK on September 04, 2020, 06:45:52 AM

NO
0.333·13·1.1

Title: Re: Ketamine MS
Post by: sharbeldam on September 04, 2020, 06:49:27 AM

thank you sir AWK, i get it now
and tbh your " NO " kinda scared me, i heard it.