Today: Brief Review of Mass Spectroscopy Discussion/Review of H-NMR, CMR Next time (our last lab lecture): Your questions Final Exam at 2:10 pm in your.

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Presentation transcript:

Today: Brief Review of Mass Spectroscopy Discussion/Review of H-NMR, CMR Next time (our last lab lecture): Your questions Final Exam at 2:10 pm in your Lab! Exam covers the material of the second half of the semester(only): “Unknowns”. Study/ review lab lectures, your labs, practice questions, sample final (in eres file). Same rules as for Midterm. No calculator needed. Spectral correlation charts will be provided.

Molecular weight: Molecular ion peak M + ? odd-numbered (N...) ? isotope peaks (Cl, Br)? Alcohols … Recognize typical fragments: H 2 O, alkyl, acyl, tropylium ion … Mass Spectrometry Summary (Examine your Unknown #3 Mass spectrum!)

Weights of common fragments or neutral losses

Benzoic acid 3-methoxytoluene phenetole Salicylaldehyde This is the mass spectrum for which compound? M + =

Basic Information from Proton NMR (Examine your Unknown #3 H-NMR spectrum!) Number of signals Number of different types of protons Chemical shifts Type of environment for protons Integration Ratios of numbers of protons Splitting of Signals Information about neighboring protons NMR Solvent peaks …..

Simple hydrocarbon protons absorb in the region Protons on a carbon adjacent to a carbonyl are shifted to 2 ppm (acetone!) Electronegative atoms (O, halogens) move protons to 3-4 Alkene protons are shifted to 5-6 Aromatic protons to 7-8 (Amide CONH is also found here) Aldehydic protons to 10 Most highly shifted protons are generally those of carboxylic acids, with values of 12 Can also be far downfield: phenol OH, enol Proton NMR Chemical Shifts (  ) For 1 H NMR, the scale generally extends from 0-12 ppm (TMS standard)

Proton NMR Chemical Shifts for Common Functional Groups For 1 H NMR, the scale generally extends from 0-12 ppm

Proton NMR Common Splitting Patterns AB J’s (Hz)!

Practice Proton NMR

(Examine your Unknown #3 CMR spectrum!) Simple methyl carbons tend to absorb in the region 15-30, simple methylene carbons are shifted to Electronegative atoms (O, halogens) move attached carbons to Alkyne carbons are shifted to 70-90, alkene carbons to , aromatic carbons to Most highly shifted carbons are generally those of carbonyls, with values of C NMR Chemical Shifts for Common Functional Groups Range ppm (TMS standard) Proton noise-decoupled Integration not useful

13 C NMR Chemical Shifts for Common Functional Groups

13 C NMR Practice How many types of C ? Indicated by how many signals there are in the spectra (solvent peaks ….) What types of C ? Indicated by the chemical shift of each signal

13 C NMR Practice Symmetry!

13 C NMR Practice How many signals would you expect in the 13 C spectrum of o-xylene m-xylene p-xylene?

Next time (our last class): Your questions Final Exam at 2:10 pm in your Lab (Begin studying early!) Exam covers the material of the second half of the semester: “Unknowns”. Study/ review lab lectures, your labs, practice questions, sample final. Same rules as for Midterm. No calculator needed. Spectral correlation charts will be provided. How your C336 class grade is calculated ….