TEST BANK For Organic Chemistry Mechanistic Patterns, 2nd
Edition by Ogilvie, Ackroyd, Verified Chapters 1 - 20, Complete
Newest Version
What is the percentage of s and p character in an sp orbital? - ANSWER: sp orbitals
have 50% s character and 50% p character
What do we get upon mixing 2s and 2px, 2py and 2pz orbitals? - ANSWER: 4 sp3
hybrid orbitals arranged at 109° to eachother (tetrahedral). sp3 hybrid orbitals have
25% s character and 75% p character.
Rules for interactions between filled and empty orbitals - ANSWER: 1. Two orbital
two electron interactions are stabilising
2. The stabilisation is greatest if a filled orbital and an empty orbital are close in
energy
3. Interacting orbitals must have good alignment and overlap efficiently
4. Interacting orbitals must have suitable (i.e matched) symmetry
What is Bredts rule? - ANSWER: A bridged bicyclic compound cannot have a double
bond at a bridgehead position unless one of the rings contains at least eight carbon
atoms
Transition states vs intermediates - ANSWER: Transition state structures have
partially formed bonds and do not exist for a finite time so cannot be isolated or
observed. they are the maxima on the reaction diagram.
an intermediate is the product of one step and the reactant for the next step.
it exists between energy barriers and it theoretically can be isolated or observed,
intermediates have fully formed bonds
What is ΔG°? - ANSWER: The Gibbs free energy change for a reaction
How do we calculate the Gibbs free energy change for a reaction? - ANSWER: ΔG° =
ΔH° - TΔS° or ΔG° = -RTlogeK where K = the equilibrium constant
What does the Gibbs free energy (ΔG°) change tell us? - ANSWER: determines the
ratio of products:starting materials when the reaction is under thermodynamic
control, i.e. the reaction reaches equilibrium
If we consider the equation A <--> B, how do we work out Keq? - ANSWER: Keq =
[B]eq/[A]eq where [A]eq = concentration of A at equilibrium
If at equilibrium there is more B than A, then what is Keq? - ANSWER: If at
equilibrium there is more B than A, then Keq > 1
so, log Keq > 1
, So, ΔG° = -RTlogeKeq < 0
If there is more A than B then what is ΔG°? - ANSWER: ΔG° > 0
If [A]eq = [B]eq, then - ANSWER: Keq=1
So, log Keq = 0
So, ΔG°=0
Why can a small change in ΔG° make a large difference in Keq? - ANSWER: Since, ΔG°
= -RTlogeKeq
What does it mean if ΔG° is negative? - ANSWER: then the product(s) are favoured
over reactants at equilibrium
What causes ΔG° to be negative? - ANSWER: ΔH° is negative because the bonds in
the product(s) are stronger than those in the reactant(s), or because there is less
strain in the product(s) than the reactant(s).
ΔS° is positive because there is greater freedom of motion (i.e. less order) in the
product(s) than in the reactant(s)
How do polar solvents solvate molecules? - ANSWER: Polar solvents cluster around
charges in reactants and products (solvation) so that the charge is delocalised.
How does the solvent affect the position of equilibrium? - ANSWER: Breaking the
charge-dipole (or dipole-dipole) interactions of the solvated reactant(s) increases
DH° (favouring reactants), while forming the charge-dipole (or dipole-dipole)
interactions in the solvated product(s) decreases DH° (favours products).
if the products are more polar than the reagents, then a polar solvent will favour the
formation of the products. Conversely, if the reactants are more polar than the
products, then a polar solvent will disfavour product formation
What is a protic solvent? - ANSWER: Protic solvents contain O-H or N-H bonds and
solvate positive charges and negative charges, e.g. solvents such as H2O or CH3OH.
What is an aprotic solvent? - ANSWER: Aprotic solvents do not contain O-H or N-H
bonds and will only solvate positive charges, e.g. solvents such as DMSO, i.e.
(CH3)2SO, and acetonitrile, CH3CN
The degree to which a solvent solvates charges depends on what? - ANSWER: The
polarity of that solvent
In what scenario would we choose to use a polar solvent? - ANSWER: Generally, a
polar solvent must be used if one of the reactants is an ionic solid or it will not
dissolve
What is the dielectric constant? - ANSWER: The dielectric constant is a measure of a
solvents ability to solvate (delocalise) charge. i.e the polarity
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