Aromatics No branching = strong M+. Often see M++.

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Presentation transcript:

Aromatics No branching = strong M+. Often see M++. m/z 77, 51 = phenyl (monosubst benzene) Most prominent peaks are due to beta cleavage of branches to benzylic (really tropylium.)

Alcohols Weak M+. Often nonexistent for 2º, 3º. M-18 (water) (rearrangement using δH?) M-33 (water + methyl) (1º) β cleave largest branch to oxonium

Ethers Homologous series is +2 (31, 45, 59….) β cleave to oxonium C-O cleavage to R+ Acetals β cleave to very stable oxonium with 2 res structures  no M+ seen

Carbonyl Compounds α cleave to acylium ion (vs 43, 57, 71 peak) McClafferty rearrangement if γ H is present (neutral or pos alkene fragment) M-28, M-42, M-56 28, 42, 56…