CHEM 3331 1nd Edition Lecture 26Outline of Last Lecture I. Reaction with PX3 or PX5II. Reaction with thionyl chlorideIII. DehydrationIV. Reaction of diolsV. Formation of estersOutline of Current Lecture I. Mass spectrometryII. Electromagnetic spectrumIII. Infrared spectroscopyCurrent LectureI. Mass spectrometryThrough combustion we can determine the ratio of carbon to hydrogen. However, we need to know the mass to determine the proper structure, information about functional groups, and carbon skeleton. Mass is provided by mass spectrometry. Functional groups provided by infrared spectroscopy. Carbon skeleton provided by NMR spectroscopy. In mass spectrometry, a sample is heated and the vapors are hit with electrons creating a cation. The cation will travel to a negatively charged accelerator plate. It will then enter a curvedmagnet, deflecting it from a straight path. You can choose the mass of particles will that pass through the magnets to a detector plate. This gives a ratio of mass to charge (m/z). the highest peak relative to m/z axis is the cation (molecular ion). The other lines provided are fragmentation ions. The molecular ion needs highest m/z not the highest intensity. Mass spectrometer detects only charged particles. From this we can determine:a) molecular massb) prescence of N (will tell you only if you have an odd number of N)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.c) presence of Br or Cl ( these are mixtures of two odd numbered masses. Br= 79 or 81. Cl=35 or37. Br is in a 1:1 ratio whereas Cl is a 3:1 ratio between M and M+2).Mass spectrometry cannot tell difference between structure or where functional groups are. II. Electromagnetic SpectrumE=hv= h(c/λ)Gamma rays (10^-16, 10^-18m) xrays (10^-11, 10^-8) UV (10^-9,10^-7)visible(300-700nm) infrared (10^-6,10^-3) microwave (10^-3, 10^-1) radiowave (1,100m)Nm=10^-9mGamma rays and xrays are destructive. UV induce a change in e- transition. Infrared vibrates molecules along their bonds. Microwaves induce rotation. Radiowaves change the spin of e-.III. Infrared spectroscopy Infrared light= 2500-25000nm= 400-4000 (1/cm).Water glass and snow absorb infrared light so NaCl is used for the lens.V= a(k/μ)^1/2 μ=reduced mass= m1m2/m1+m2V(C-O)=1100 V(C=O)=1700 V(C-H)=3000 V(C-C)=1200 V(C-D)=2100From infrared spectroscopy we gain a graph of v vs. transmittance. No two molecules have the same fingerprint region. We have to analyze by comparison to computer database.R2C=01630-1820 R2C=CR21600-1800 (moderate to weak) -OH3200-3650-NH2 3100-3550 -CH SP3 2800-3000 SP23000-3100 SP3300H-C=O
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