Chemical Shift

Carbon-13 Spectra How many C-13 signals? Which signals are further upfield? Can the compounds be differentiated?

Correlation Chart Same number of signals Occur in different areas of spectrum Predictable shifts

Chemical Shift Tables Complex vs simple Basics: – Alkane: 5-45ppm – C-Q: 40-70ppm – sp: ppm – sp 2 : ppm – Carbonyl: ppm

Predict C-13 Chemical Shifts If carbon fits two categories, choose higher shift

More subtle points Inductive effects Additive effects More substituted sp 3 carbon is further downfield

More subtle points Carbonyls – Above 200ppm, ketone and aldehyde – Below 200ppm, O=C-Q – Explain by shielding and resonance

More subtle points Alkene vs Alkyne

Which Structure(s) Fit? CDCl 3 TMS absent

Which Structure Fits?

C3H8OC3H8O

Proton NMR Shifts

Basic Correlation Chart How many 1 H signals? Shift? Proton NMRChemical Shift (ppm) alkane CH alkane CH alkane CH1.7 X=C-C-H (Ph-C-H or O=C-C-H) 2-3 O-C-H X-C-H 3-4 (sp 2 ) C=C-H5-6 Ph-H7-8 O=C-H9-10 O=C-O-H10-12 O-H, N-H1-5

Common “exceptions” Phenyl protons give one “signal” even if nonequivalent

Common “exceptions” Exchangeable protons are broad and small Washed away with D 2 O