4 - Intro

4 - Intro - Jim Heath 16 Noyes heath@caltech.edu 1 A few...

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1 Jim Heath 16 Noyes heath@caltech.edu
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2 A few comments: 1. You won±t 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 ² 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.
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3 Please ask questions!!! Stop me and raise your hand if you don±t 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.
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4 Fri & next week Today & tomorrow & Thursday Also, Mass spectrometry next week
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5 Spectroscopy Units wavenumbers cm -1 A wavenumber is simply 1/ O , with O in cm±s. Recall that Energy = E = h Q = hc/ O , so 1/ O (= cm -1 ) is an energy Q , 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 ) = Planck±s constant B E Light is electromagnetic radiation O time (wavelength)
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6 Spectroscopy Units wavenumbers cm -1 A wavenumber is simply 1/ O , with O in cm±s. Recall that E = h Q = hc/ O , so 1/ O (= cm -1 ) is an energy Q , 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 ² 25000 cm -1 § 1.5 ² 3 eV eV±s 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 ) = Planck±s constant
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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 O , cm -1 , s -1 , or eV±s WHY? Discreet (or quantized) absorption or emission spectra
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8 The pickle light bulb
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9 A guitar string and its resonant frequen- cies. Notice that all frequencies are integral multiples of the funda- mental frequency, shown at the bottom of the drawing. 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 O = h/mv L L Particle-in-a-Box Analogy (Guitar String) h = 6.626e-34 J·s (kg m 2 s -1 ) = Planck²s constant m e = mass of an electron = 9.109e-31 kg Louis DeBroglie 1892-1987 (was a Duke) Ph.D. Thesis: any moving particle or object has an associated wave.
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4 - Intro - Jim Heath 16 Noyes heath@caltech.edu 1 A few...

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