[beheada]

I am completely confused by this question. It reads:

"Two products are obtained from the reaction of 2-pentene with water and a trace amount of sulfuric acid. The mass spectra of each of these products is shown below. Identify the compounds responsible for the spectra. EXPLAIN how you arrived at your answers for each choice."

Then it gives the spectra.

Spectra A: Has a molecular ion peak (parent peak) @ 70 with a 71/69 beside it. The other largest peaks are 45, 41, 31, 27, and the base peak (highest intensity) is 59.

Spectra B: The molecular ion peak looks like 73, with a hint of something at 70/71/69. The base peak is 45. Other peaks of interest are 27, 31, and 55.

I am trying to come up with the two products of 2-pentene + H2O in acid.
I am assuming that the alkene undergoes hydration and gains a hydroxyl group on the more substituted carbon (markovnikov). This grants me 3-pentanol with a M+=88. The other minor product would then be the non-markovnikov 2-pentanol, which is the same M+=88 value.

Now I go to the alpha cleavages and dehydrations. Let's say markov is compound 1 and nonmarkov compound 2.
For compound 1:
Alpha Cleavage yields: CH2CH3 (radical - 29) + CH3CH2CH-OH (cation - 59) and vice versa...
CH3CH2CH-OH (radical - 59) + CH2CH3 (cation - 29)
Dehydration yields: 2-pentene (cation+radical - 70) + H2O (18)

For compound 2:
Alpha Cleavage yields: CH3 (radical - 15) + HO-CHCH2CH3 (cation - 73) and...
CH3CH-OH (radical - 45) + CH2CH2CH3 (cation - 43)
Dehydration yields: 1-pentene (70) + H2O (18) and...
3-pentene + H2O (18)

Therefore with the following information I drew my conclusion:

Spectra A has a base peak @ 59, which corresponds to the alpha cleavage of the markovnikov compound 1.. 3-pentanol.

Spectra B has a base peak at 45 meaning that the most stable fragmentation would be the ethanol cation produced during alpha cleavage. It also has fragments at 43 and 73 corresponding to points on spectra B.

All of this I believe is correct, but what troubles me are the other peaks that are unaccounted for. For example, Spectra A/Compound 1 has peaks at 41 and 31 which I haven't accounted for. Likewise, none of the parent peaks (molecular ion peaks) of the two products 2-pentanol and 3-pentanol are evident in the Spectra, since they are 88.

What am I doing wrong? Because I am stumped, tired and hungry.

.rayfe- out

[Dan]

Here are some possibilities, but I'm no MS expert,

41  Propene radical/ion (Me-CH=CH)
31 Maybe a long shot, (H₂COH) radical/ion

you also don't seem to have assigned 27 or 55

My ideas:

27 (H₂C=CH)
55 (MeCH₂CH=CH)