Ch1b2010_week2_ab

Ch1b2010_week2_ab - 1 Jim Heath 16 Noyes [email protected] 14...

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Unformatted text preview: 1 Jim Heath 16 Noyes [email protected] 11 12 14 15 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 – 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 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. 4 Fri & next week Today & tomorrow & Thursday Also, Mass spectrometry next week 5 Spectroscopy Units wavenumbers cm-1 A wavenumber is simply 1/ λ , with λ in cm’s. Recall that Energy = E = h ν = hc/ λ , so 1/ λ (= cm-1 ) is an energy ν , 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 λ time (wavelength) 6 Spectroscopy Units wavenumbers cm-1 A wavenumber is simply 1/ λ , with λ in cm’s. Recall that E = h ν = hc/ λ , so 1/ λ (= cm-1 ) is an energy ν , 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 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 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 λ , cm-1 , s-1 , or eV’s 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 λ = h/mv L L Particle-in-a-Box Analogy (Guitar String) h = 6.626e-34 J · s (kg m 2 s-1 ) = Planck’s constant m e = mass of an electron = 9.109e-31 kg Louis DeBroglie 1892-1987...
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This note was uploaded on 10/27/2010 for the course CH 1b taught by Professor Natelewis during the Winter '09 term at Caltech.

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Ch1b2010_week2_ab - 1 Jim Heath 16 Noyes [email protected] 14...

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