Use a Walsh diagram to predict whether the shape of the CH_3^+ carbocation intermediate in an S_N I reaction will be trigonal planar or trigonal pyramidal. How does the molecular geometry of the CH_3^+ intermediate explain the stereochemical product distribution (retention, inversion, or racemic) in an S_N I reaction?
Part 2: Construct the three-dimensional geometry for the molecules listed in Table 2.
Table 2: Molecular Models
Molecule (central atom is underlined)
Shape Name
Bond Angle
Bond Angles
(more than one may be possible)
CO2
Linear
AlCl3
Trigonal Planar
H2O
Bent
NH3
Trigonal pyramidal
CCl4
Tetrahedral
PCl5
Trigonal bipyramidal
SF6
Octahedral
Post-Lab Questions:
1. What is the molecular geometry (shape) of the methane molecule (CH4)? Explain completely why all the bond angles in methane are equal.
2. What is the molecular geometry (shape) of the chloromethane molecule (CH3Cl)? Explain completely why NOT all of the bond angles in chloromethane are equal.
3. Chloromethane can be thought of as resulting from methane via the replacement of one Hydrogen atom with a Chlorine atom. Subsequent replacements of H with Cl yield dichloromethane (CH2Cl2), trichlormethane (CHCl3) and tetrachlormethane (CCl4). Which of these three previous molecules will have all bond angles equal to each other? Explain completely.
4. Sketch the molecular shape of the compounds in the table below. Be sure to identify the bond angles. H2 Cl2 SO2 NH3 MoF6
