Synthesis practice solutions1

Synthesis practice solutions1 - 1 H NMR: two distinct...

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S y n t h e s i s P r a c t i c e P r o b l e m s Week of 4/16/07 SOLUTIONS N O T E : There may be other acceptable ways to synthesize these compounds besides the pathways below. Trying to find other pathways to the product is good practice! W.U. HBr Br LDA (2eq) H H H 2 Pd-C 1. LDA Br H 1. DSB 2. H 2 O 2 , H 2 O, NaOH H O OH 2. LDA Br H HBr (xs) Br Br Br
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3. Br LDA H 2 Lindlar's Br 2 CH 3 OH Br OCH 3 H H 4. Br 1. BH 3 /THF 2. H 2 O 2 , H 2 O NaOH Br OH LDA O 5. HBr Br LDA H 3 O + O 6. HBr 45 o C Br H + CH 3 OH Br OCH 3 LDA OCH 3
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S p e c t r o s c o p i c d i f f e r e n c e s b e t w e e n S . M p r o d u c t : W.U. – IR: Double bond stretch (~1600 cm -1 ) disappears 1 H NMR: Loss of vinyllic proton signals (4.5-6.5ppm), many new signals upfield 1. IR: Appearance of carbonyl stretch of aldehyde and OH stretch 1 H NMR: loss of alkyne protons, appearance of aldehyde proton (~8- 10ppm) and protons next to OH group 2. IR: Difficult to tell from this alone, most significant differences are in the fingerprint region. Although you do have the appearance of the C-H (sp 3 ) stretch. 1 H NMR: appearance of protons in the 2.5-4.5ppm region from those next to the bromines 3. IR: Difficult to tell- most stretches are in the fingerprint region
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Unformatted text preview: 1 H NMR: two distinct protons in the 2.5-4.5ppm region one next to the bromine, one next to the methoxy group. 4. IR: Loss of C=C @ ~1600cm-1 and C-H (sp 2 ) @ ~3050cm-1 ; all other significant differences would be located in the fingerprint region. 1 H NMR: Loss of vinyllic protons, loss of protons next to bromine, appearance of two new signals in 2.5-4.5ppm region from two sets of protons adjacent to oxygen 5. IR: Disappearance of C=C stretch, appearance of C=O stretch, disappearance of C-H (sp 2 ) 1 H NMR: loss of vinyllic protons, appearance of protons next to carbonyl group (1.5-2.5ppm) 6. IR: Loss of C=C, C-H(sp 2 ), appearance of alkyne signal 1 H NMR: loss of vinyllic protons, appearance of alkyne proton, protons of carbons two bonds away from oxygen will be deshielded slightly....
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Synthesis practice solutions1 - 1 H NMR: two distinct...

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