Question

the mass spectrum of ethanol consists of lines at m/e = 15,28,31,45 and 46.
Write the formula of all the ions responsible for these lines
@Abhisar

Answer 1

hope u can help me out

Answer 2

@ParthKohli

Answer 3

@Somy

Answer 4

ah no i don't really know this.. im sorry :(

Answer 5

Since there are only a few fragmentation patters for small molecules, like ethanol, you can play around with the molar masses of the atoms and guess them.

It makes it easier if you take inventory
6 H 1 g/mol
2 C 12 g/mol
1 O 16 g/mol

Now we just look for combinations that give you those mass-to-charge ratios

15 m/e -> 1 C + 3 H = 12 + 3 = 15

so this is \(CH_3^+\)

28 m/e -> 2 C + 4 H = 24 + 4 = 28

this is \(C_2H_4^+\), it looks like



you might also think that you can have 1 O + 1 C because it also adds up to 28, but that's unlikely because the ion needs to be stable. Try the rest

Answer 6

31 m/e = \[C _{36} H _{5}\]
Is it correct
@aaronq

Answer 7

\(C_{36}\)? but you only have 2 carbons

Answer 8

can u show how to get the correct answer for m/e 31

Answer 9

\[CH _{2}\] ?

Answer 10

hm lets see if we have 1 O and 1 C, then were at 16+12=28, if we add 3 H's then were at 31.

Answer 11

remember that were working with the molar masses of the atoms, they must add up to the values given.

Answer 12

ok, how do I add 3H's

Answer 13

each H has a mass of 1, so 28 +3 = 31. When you're learning this you should always be working with pictures to aid you visualize the fragments.

Answer 14

Understood

Answer 15

Thanks @aaronq

Answer 16

No problem, try it again, if you dont get it i'll look at it later. I have to go

Answer 17

m/e 45