lecture 6 sp 09 given - Lecture 6 Chemistry 310N Chemistry...

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Unformatted text preview: Lecture 6 Chemistry 310N Chemistry 310N Organic Chemistry II for Prehealth Professionals Unique number: 53185 Tu,Th 12:30-2:00 pm, Welch 2.224 rofessor: Jonathan Sessler Ph D Professor: Jonathan Sessler, Ph.D. sessler@mail.utexas.edu Notes: Homework 2 due; homework 3 will be posted Thurs and old exams soon. 13 C NMR spectroscopy, although in the book, will not be on Exam I Exam 1 will cover chapters 12 and 13 in detail and chapter 14 in cursory fashion. It is next Thursday in class! Office hours in Prof. Sesslers office (Wel 5.428) ca. 2-4 pm today. Office hours in Wel. 3.422 2:00-3:30 pm on Tuesday Last time, Dr. Rambo explained. ignal Splitting; the ( + 1) Rule Signal Splitting; the ( n 1) Rule Peak: Peak: The units into which an NMR signal is split; doublet, triplet, quartet, multiplet, etc. Signal splitting: Signal splitting: Splitting of an NMR signal into a set of peaks by the influence of neighboring nonequivalent hydrogens. ( n + 1) rule: + 1) rule: If a hydrogen has n hydrogens nonequivalent to it but equivalent among themselves on the same or adjacent atom(s), its 1 H-NMR signal is split into ( n + 1) peaks. Origins of Signal Splitting Magnetic field of H Magnetic field of H b subtracts from the applied subtracts from the applied H H field; H field; H b signal appears at signal appears at a higher applied field a higher applied field b H a Magnetic field of H Magnetic field of H b adds adds to the applied field; H to the applied field; H a signal appears at a lower signal appears at a lower H b g p p g p p applied field applied field Rememberit is the NET NET field that counts hysical Basis for ( 1) Rule Physical Basis for ( n + 1) Rule oupling of nuclear spins ( generally in Hz) is mediated Coup g o uc ea sp s ( J ; ge e a y ) s ed ated through intervening bonds. H atoms with more than three bonds between them generally do not exhibit noticeable coupling. For H atoms three bonds apart, the coupling is referred to as vicinal coupling . rigins of Signal Splitting Origins of Signal Splitting The origins of signal splitting patterns. Each arrow represents an H b nuclear spin orientation. ignal Splitting Signal Splitting Pascals triangle. As illustrated by the highlighted entries, each ntry is the sum of the entry is the sum of the values immediately above it to the left and the right. ignal Splitting (n + 1) Signal Splitting (n + 1) Problem Problem: Predict the number of 1 H-NMR signals and the splitting pattern of each. CH 3 CCH 2 CH 3 O (a) CH 3 CH 2 CCH 2 CH 3 O (b) CH 3 CCH( CH 3 ) 2 O (c) Please do these as a quiz and turn them in at the end of class; include your name and UT ID on the paper. Note: (b) is a gimme since it is on the next slide(!) and problem (c) will make an appearance later on in lecture, assuming we get that far. So, dont sweat this!! rigins of Signal Splitting Origins of Signal Splitting The quartet-triplet 1 H-NMR signals of 3-pentanone showing the original trace and a scale expansion to show the signal plitting more clearly splitting more clearly. ignal Splitting (n + 1)...
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This note was uploaded on 06/15/2009 for the course CH 53185 taught by Professor Sessler during the Spring '09 term at University of Texas at Austin.

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lecture 6 sp 09 given - Lecture 6 Chemistry 310N Chemistry...

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