{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

36_562ln08 - MIT OpenCourseWare http/ocw.mit.edu 5.62...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
MIT OpenCourseWare http://ocw.mit.edu 5.62 Physical Chemistry II Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
5.62 Spring 2008 Lecture #36 Page 1 Rates of Unimolecular Reactions: RRKM Consider a unimolecular reaction: A products isomerization CH 3 NC CH 3 CN decomposition (with barrier to recombination) C 2 H 5 Cl C 2 H 4 + HCl In order to occur, these reactions must overcome a barrier, E 0 . They can be activated to E* > E 0 by collision, overtone pumping, infrared multiphoton excitation, optical excitation followed by Internal Conversion, or Stimulated Emission Pumping. A molecule becomes activated, either by absorption of a photon or by a collision. The activated molecule has a definite E and J. If E > E 0 , where E 0 is the energy of the zero- point-energy-dressed barrier for the unimolecular process: We want to predict the rate of the reaction. reaction coordinate A(bound) v = 0 E 0 products E* Standard mechanism (from 5.60) activation A + M A* + M k 1 deactivation A* + M A + M k –1 revised 4/24/08 11:40 AM
Image of page 2
5.62 Spring 2008 Lecture #36 Page 2 irreversible decay into products A* products k 2 Steady state for A* d A * [ ] dt = k 1 [A][M] ! k ! 1 [A*][M] ! k 2 [A*] = 0 [A*] SS = k 1 [A][M] k ! 1 [M] + k 2 d[products] dt = k uni [A] = k 2 [A*] = k 1 k 2 [A][M] k ! 1 [M] + k 2 " k uni = k 1 k 2 [M] k ! 1 [M] + k 2 = k 1 k 2 k ! 1 1 + k 2 k ! 1 [M] ( ) use this form of k uni below ! " ######### “Unimolecular” rate is actually pressure-dependent.
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern