102218 Character Tables and Vibrational Spec.pdf - Tentative Agenda this week • Normal office hours this week(as in the syllabus you can pick up your

102218 Character Tables and Vibrational Spec.pdf -...

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Tentative Agenda this week: Normal office hours this week (as in the syllabus): you can pick up your exam at any of the office hours Note: Changes/considerations to exam grading must be requested before you leave the room on the day you pick up your exam. Note : We are not accepting full exam regrade submissions. Today: Review of reducible representations for stretching modes Going from reducible to irreducible representations end 10 minutes early to hand back MT1 Wednesday: Brief exam review (JIT question will have an optional question to vote for problems to see in class) M-CO stretching modes via reducible/irreducible representations Friday: Molecular Orbital Theory Need to be solid on symmetry, character tables, reducible/irreducible reps Sapling homework is basic concepts, not exam-like questions
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Resources on Canvas
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i-clicker/REEF question: What are your impressions of midterm 1 ? A B C D E 3 Too hard Not hard, but too long Easier than I was expecting The level that I expected Totally unreasonable
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i-clicker/REEF question: How do you feel about how you did in midterm 1? A B C 4 Better than I expected Worse than I expected About how I expected A B C D F A B C D F 0 20 40 60 % of students Standard Bell Curve Midterm 1
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Self-Assessment Take a few minutes to answer the following questions: What helped me prepare most for MT1? What thing(s), if any, do I commit to doing to prepare for MT2? 5
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The synthesis and characterization of cubane was reported in 1964 by Philip Eaton and Thomas Cole in the Journal of the American Chemical society (JACS) 1964, 86, 3157-3158. Cubane, C 8 H 8 , has 42 vibrational degrees of freedom, but only three IR peaks. Cubane belongs to the octahedral point group. What are(is) the possible symmetry label(s) of the IR active modes. O h E 8C 3 6C 2 6C 4 3C 2 =(C 4 ) 2 i 6S 4 8S 6 3 h 6 d linear functions, rotations quadratic functions A 1g +1 +1 +1 +1 +1 +1 +1 +1 +1 +1 - x 2 +y 2 +z 2 A 2g +1 +1 -1 -1 +1 +1 -1 +1 +1 -1 - - E g +2 -1 0 0 +2 +2 0 -1 +2 0 - (2z 2 -x 2 -y 2 , x 2 -y 2 ) T 1g +3 0 -1 +1 -1 +3 +1 0 -1 -1 (R x , R y , R z ) - T 2g +3 0 +1 -1 -1 +3 -1 0 -1 +1 - (xz, yz, xy) A 1u +1 +1 +1 +1 +1 -1 -1 -1 -1 -1 - - A 2u +1 +1 -1 -1 +1 -1 +1 -1 -1 +1 - - E u +2 -1 0 0 +2 -2 0 +1 -2 0 - - T 1u +3 0 -1 +1 -1 -3 -1 0 +1 +1 (x, y, z) - T 2u +3 0 +1 -1 -1 -3 +1 0 +1 -1 - - Will there be any coincidences between the IR and Raman active modes? NO!
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HOW TO: determine the number of stretching modes, their symmetry and whether they are IR and Raman active e.g.
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  • Fall '08
  • SUSANKAUZLARICH

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