CHEM 141 Study Guide - Midterm Guide: Cubic Crystal System, Optical Rotation, Lone Pair
Staggered -- both sides aren't exactly the same
Eclipsed -- both sides are same
Torsion or Dihedral angles:
-angle between two bonds in a conformation
Eg. Eclipsed -- 0 degrees
Staggered/gauche -- 60 degrees
More comfortable in staggered form than in eclipsed form
--staggered form -- less PE
-energy differences are relatively small -- insignificant -- staggered and eclipsed form interconvert all the
time usually
2.3
-all-anti conformer is more stable in general -- so most diagrams are drawn in zig-zags
4.2
-chirality center -- a carbon bonded to four different groups around it
-when w-z atoms are all different Cwxyz is a chiral molecule
Mirror images but not superimposable -- enantiomers
Achiral -- equivalent
Chiral vs achiral:
-look at plane of symmetry & other stuff
Optical rotation
50-50 ratio of enanomers -- light doesn't rotate
Asymmetric mixture -- rotate partially
One type of enantiomer -- rotate
1.7
-
-electrons are delocalized in this case since they can move easily through p orbitals
-resonance -- only when there's a double bond and a single bond and lone pair
Chapter 12
Simple cubic cell -- spheres packed on top of one another
-involves 8 atoms
-each is part of 8 cubes in total (1/8th of each is in the cube)
-atoms in corners -- 1/8
-edge atom -- 1/4
-face centered -- 1/2
-body centered -- 1
Simple cubic -- only 1 atom
Body-centered -- 2 equivalent atoms -- 8 at corners and 1 in the center
Class notes
November 13, 2017
1:15 PM
part 4 notes Page 1
Document Summary
Staggered -- both sides aren"t exactly the same. More comfortable in staggered form than in eclipsed form. Energy differences are relatively small -- insignificant -- staggered and eclipsed form interconvert all the time usually. All-anti conformer is more stable in general -- so most diagrams are drawn in zig-zags. Chirality center -- a carbon bonded to four different groups around it. When w-z atoms are all different cwxyz is a chiral molecule. Look at plane of symmetry & other stuff. 50-50 ratio of enanomers -- light doesn"t rotate. Electrons are delocalized in this case since they can move easily through p orbitals. Resonance -- only when there"s a double bond and a single bond and lone pair. Simple cubic cell -- spheres packed on top of one another. Each is part of 8 cubes in total (1/8th of each is in the cube)
