Vocab

Question 1

Inductive Effects

Answer 1

The pull of electron density through sigma bonds, caused by electronegativity difference of atoms. Molecules with additional electronegative atoms help stabilize conjugate bases–thus are stronger acids.

Question 2

Periodic trends affecting acid strength.

Answer 2

Go right–>acid strength increases as electronegativity increases
Go down–>acid strength increases as the atom size increases, b/c charge is more stable over larger volumes

Question 3

S-character

Answer 3

A hybrid orbital’s fraction of the lower energy s-orbital. Higher s-character creates more stable conjugate bases thus stronger acids.
sp3 (C) –> 25% s
sp2 (C) –> 33% s
sp (C) –> 50% s

Question 4

Lewis Acid/Base

Answer 4

Acids are electron pair acceptors (electrophilic), bases are electron pair donors (nucleophilic).

Question 5

Torsional Strain

Answer 5

Increase in energy caused by eclipsing interactions.

Question 6

Steric Strain

Answer 6

Increase in energy from atoms being forced too close to one another.

Question 7

Angle Strain

Answer 7

Increase in energy when tetrahedral bond angles deviate from 109.5*

Question 8

H-H eclipsing interaction
CH3-CH3 eclipsing interaction
H-CH3 eclipsing interaction
Gauche CH3 interactions

Answer 8

H-H –> 1.0 kcal/mol
CH3-CH3 –> 2.6 kcal/mol
H-CH3 –> 1.4 kcal/mol
Gauche CH3’s –> 0.9 kcal/mol

Question 9

Chair vs Boat Cyclohexane

Answer 9

E difference is 30 kJ/mol (7.5 kcal/mol). Boat conformation is destabilized by torsional strain from eclipsed H atoms on 4 Carbons.

Question 10

Cyclohexane substituent stability

Answer 10

Larger substituents are more stable in the equatorial position b/c it has more room.

Question 11

Substituent position during ring flip

Answer 11

Substituents always stay on the same side of the ring- either above or below- during ring flip.

Question 12

Stereoisomers

Answer 12

Differ in the way atoms are oriented on space.
Cis–> two groups on same side of ring
Trans–> two groups on opposite sides of ring

Question 13

Oxidation

Answer 13

Results in the loss of electrons.
Increase in C–Z bonds
Decrease in C–H bonds

Question 14

Reduction

Answer 14

Gain of electrons.
Decrease in number of C–Z bonds
Increase in number of C–H bonds

Question 15

^G = 1.36
      = -1.36
      = 0
      = 2.8
      = -2.8

Answer 15

1.36 –> Keq = 0.1 (1 prod/10 react)
-1.36 –> Keq = 10 (10:1)
0 –> Keq = 1 (1:1)
2.8 –> Keq = 99 (99:1)
-2.8 –> Keq = 1/99 (1:99)

Question 16

Axial CH3 vs H on Chairs

Answer 16

Each axial CH3 is close to two other axial H’s (1-3 diaxial interactions). Each H-CH3 interaction is 0.95 kcal. One axial CH3 = 1.9 kcal