Ch1b2010_week2_ab

Ch1b2010_week2_ab - 1 Jim Heath 16 Noyes heath@caltech.edu...

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Unformatted text preview: 1 Jim Heath 16 Noyes heath@caltech.edu 11 12 14 15 2 A few comments: 1. You wont have to memorize much, if anything (this is not biology) 2. If you do your work with a solid effort, pass the big exams, and if your application to Caltech was legitimate, then you will pass 3. Lecture notes are VERY important!! For part 1 of this course, the powerpoint presentations of the lectures will be posted after each class (in pdf form). I may also occasionally post written lecture notes that should help focus your studying. OGN is a big, amorphous book it has good problem sets, but it covers too much material. 4. I will highlight many of our lectures by placing them into the context of real science that is being done at Caltech and elsewhere. I will cover what is important about these chemistry in context examples, and you will be asked about them regularly on quizzes. 3 Please ask questions!!! Stop me and raise your hand if you dont understand something. If you have a question, chances are about 30-80% of the people in the room have the same question. The ones who fully understand this material are not present in this room because they are not taking this course. 4 Fri & next week Today & tomorrow & Thursday Also, Mass spectrometry next week 5 Spectroscopy Units wavenumbers cm-1 A wavenumber is simply 1/ , with in cms. Recall that Energy = E = h = hc/ , so 1/ (= cm-1 ) is an energy , or frequency (cycles per second) is also an energy c 3.0 10 10 cm s-1 = 3.0e10 cm s-1 = speed of light in vacuum h = 6.626e-34 J s (kg m 2 s-1 ) = Plancks constant B E Light is electromagnetic radiation time (wavelength) 6 Spectroscopy Units wavenumbers cm-1 A wavenumber is simply 1/ , with in cms. Recall that E = h = hc/ , so 1/ (= cm-1 ) is an energy , or frequency (cycles per second) is an energy Also, electron volts eV 1 eV 8000 cm-1 = 1.6e-19 J 1 eV is the kinetic energy an electron has after being accelerated through a 1 volt electric field Visible light 13000 25000 cm-1 1.5 3 eV eVs are a manageable unit for describing visible & UV light and hence chemical bond energies c 3.0 10 10 cm s-1 = 3.0e10 cm s-1 = speed of light in vacuum h = 6.626e-34 J s (kg m 2 s-1 ) = Plancks constant 7 The photon absorption or photon emission spectrum of a molecule is discreet, or quantized True for NMR, rotational spectroscopy, infrared spectroscopy, and electronic spectroscopy Absorbance or emission , cm-1 , s-1 , or eVs WHY? Discreet (or quantized) absorption or emission spectra 8 The pickle light bulb 9 e The particle is confined by these potential energy barriers like fingers on frets An electron will exist as a wave in between these two potential barriers The deBroglie Relationship = h/mv L L Particle-in-a-Box Analogy (Guitar String) h = 6.626e-34 J s (kg m 2 s-1 ) = Plancks constant m e = mass of an electron = 9.109e-31 kg Louis DeBroglie 1892-1987...
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Ch1b2010_week2_ab - 1 Jim Heath 16 Noyes heath@caltech.edu...

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