is or is not favored at each of the three potential posilibns (oro, mc, 4. [12 p

Question

is or is not favored at each of the three potential posilibns (oro, mc, 4. [12 points] Consider the mass spectra of ketone A and ketone B shown to the right. One of these ketones gives a distinctive peak in its mass spectrum at me = 91; the other ketone gives a distinctive peak in its mass spectrum at me = 105. (a) Identify which one of these ketones gives the peak at m/e 91 and provide a CH-CHy CH CCHy ketone A ketone B Lewis structure that corresponds to the peak at m/e = 91. (b) Identify which one of these ketones gives the peak at m/e 105 and provide a Lewis structure that corresponds to the peak at mle = 105 Screen Shot 2015-06-23 at 9.45.09 PM each of the following reactions. ebeB kebme B 4b eine gf 8 f9

Explanation / Answer

m/e is ratio of mass of ion to charge on it. Here m is relative formula mass of + ve ion & e is charge on it ((virtually all ions have charges of z = +1, so sorting by the mass to charge ratio is the same thing as sorting by mass).Both these ketone ionised as

C6H5COC2H5----->C6H5COC2H5.-----> C6H5CO+ + +C2H5

molecule (ionisation)          moleculer ion     fragmentation

C6H5CH2COCH3----->C6H5CH2COCH3.-----> C6H5CH2+ + +COCH3

molecule (ionisation)                moleculerion--fragmentation

In mass spectroscopy first molecule is ionised and then moleculer ion and their fragment is subjected to mass analyser where they are separated according to their mass.

For ketone A

C6H5COC2H5.(m/z=134)------>C6H5CO+(m/z=105) + C2H5+(m/z= 29)

for ketone B

C6H5 CH2COCH3.(m/z= 134)-----> C6H5CH2+( m/z= 91) + COCH3(m/z=43)

m/z ratio is used to know the formula mass of given moleculerion and so the molecule.

these fragment can further breakes into smaller ions.this is apply for every mlecule.

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