2444-090211

2444-090211 - P(73(100 P 1(74(4.80 P 2(75(0.10 odd mass so...

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Unformatted text preview: P (73) (100) P+1 (74) (4.80) P+2 (75) (0.10) odd mass, so 1 nitrogen, so P+1 = 4.80 = 1.11(#C) + 0.38 (1 N) #C = 4.80 – 0.38 = 4.42/1.11 = 3.98 = 4 C 4 N P+2 = 0.1 = [(1.11)(4)] 2 /200 + 0.20 #O 0.1 = 0.098 + 0.2 #O #O = 0.1 – 0.1 / 0.2 = 0 no O Cannot see H in mass spec, therefore obtain H by difference from the parent ion (73) 4 C x 12 = 48 + 1 N x 14 = 62 73 – 62= 11, so 11 H ????? C 4 H 11 N Example 2 Remember the alkane formula C n H 2n+2 = maximum number of H for a molecule For C4, C 4 H 10 , should be more than 10H, but this has N, with an odd valence therefore, use C n H 2n+3 so 11 is OK P (162) (100) P+1 (163) (6.66) P+2 (98) even mass, so 0 nitrogen, so P+1 = 6.66 = 1.11(#C) + 0.38 (0 N) #C = 6.66 /1.11 = 6 C 6 P+2 =98% of P = Br assume no oxygen, so C 6 Br Cannot see H in mass spec, therefore obtain H by difference from the parent ion (162) 6 C x 12 = 72 + 1 Br x 79 = 151 (note use 79 isotope for Br parent) 162 – 151 = 11, so 11 H ????? Remember the alkane formula C n H 2n+2 = maximum number of H for a molecule replace H with Br - use alkane formula For C6, C 6 H 14 , so there cannot be more than 14H so 11 is OK C 6 H 11 Br Example 3 Fragmentation of the parent can give structural clues OH P – 18 loss of water loss of methyl P – 15 O P – 29 O !-cleavage m/ z 29 M-18 = alcohol M-15 = parent had a methyl group !-cleavage and M-29 = an ethyl group next to a functional group or heteroatom Common Fragmentations: M – ? O• O• H : : O : H O : H • • 1 2 + 1 O : O : McLafferty rearrangement !-cleavage 3 4- C 4 H 9-CH 3 Ketones undergo !-cleavage next to carbonyl If chain is long enough - McClafferty rearrangement occurs McClafferty Rearrangement Actual Mass Spectra We now have an unknown, and mass spectrometry gives us the molecular weight and the empirical formula Before we can identify the molecule, we must know the functional group We use infrared spectroscopy In mass spectrometry, so much energy is applied to the molecule that it fragments. It is also possible to apply only enough energy to make the molecule vibrate but not break bonds. enough energy to make the molecule vibrate but not break bonds....
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2444-090211 - P(73(100 P 1(74(4.80 P 2(75(0.10 odd mass so...

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