Exam 3 Terms

Question 1

chiral

Answer 1

non-superimposable molecule, does not have a plane of symmetry

Question 2

achiral

Answer 2

superimposable molecule, a plane of symmetry, no chiral centers

Question 3

z

Answer 3

same (zame)

Question 4

e

Answer 4

opposite (epposite)

Question 5

meso compound

Answer 5

has at least 2 stereocenters, and a plane of symmetry, they are achiral

Question 6

r

Answer 6

clockwise

Question 7

s

Answer 7

counter clockwise

Question 8

lowest priority group has to be ___ thus changing the r & s configuration to its opposite

Answer 8

on a dash

Question 9

enantiomers

Answer 9

mirror images of each other

Question 10

diasteriomers

Answer 10

not mirror images of each other

Question 11

chiral center

Answer 11

a carbon with 4 different groups

Question 12

constitutional isomer

Answer 12

same molecular formula, different order of connectivity

Question 13

stereoisomers

Answer 13

same molecular formula and constitution, different spatial arrangement

Question 14

cis

Answer 14

same side of double bond, same side of molecule single bond

Question 15

trans

Answer 15

different sides of double bond, different side of molecule single bond

Question 16

optically active

Answer 16

are chiral molecules that do not have a plane of symmetry

Question 17

A compound that converts a mixture of two enantiomers into diastereomers by reacting with them is called a:

Answer 17

resolving agent

Question 18

irreversible reactions

Answer 18

products have a higher pka than reactants

Question 19

by decreasing the temperature, the rate

Answer 19

decreases for all reactions

Question 20

for a decrease in entropy

Answer 20

the reaction converts two molecules of reactants into one molecule of product. This reaction, therefore, causes a decrease in the total number of molecules. Such a process represents a decrease in entropy (ΔS < 0).

Question 21

endergonic reactions

Answer 21

are not spontaneous and are positive from reactants to products

Question 22

an increase in entropy

Answer 22

signifies an increase in molecules present

Question 23

If ΔG is negative

Answer 23

the reaction will favor products over reactants, and Keq will be greater than 1. Since ΔG is negative, Keq > 1.

Question 24

If ΔG is positive

Answer 24

the reaction will favor reactants over products, and Keq will be less than 1. Since ΔG is positive, 0 < Keq < 1 since Keq is never less than 0.

Question 25

Why can’t a polar aprotic solvent stabilize anions in a substitution reaction?

Answer 25

The electron poor region of the solvent is inaccessible to an anion due to sterics

Question 26

In an E2 reaction, the _______________ is the more substituted alkene while the _____________ is the less substituted alkene. The product distribution __________________________________.

Answer 26

Zaitsev product; Hofmann product; is difficult to predict due to a number of factors

Question 27

In general, since E2 mechanisms are ___________ , they will occur in ______ step(s).

Answer 27

concerted: 1

Question 28

a strong nucleophile will

Answer 28

A strong nucleophile will increase the rate of a SN2 substitution reaction.

Question 29

Which type of solvent is best for SN1 reactions?

Answer 29

Protic solvents because they can stabilize both ions well.

Question 30

For SN2 processes, polar _________ solvents enhance the rate of reaction, but for SN1 processes, polar __________ solvents are better since they stabilize the ionic intermediates and transition states.

Answer 30

Aprotic ; Protic

Question 31

Polar aprotic solvents do not have:

Answer 31

A hydrogen atom connected directly to an electronegative atom.

Question 32

In general, an E2 reaction requires the use of a

Answer 32

strong base

Question 33

E2 reactions require the use of a __________ base. An alcohol (ROH) __________ be used as a substrate in an E2 reaction, because an OH group is a poor leaving group and cannot be protonated under strongly basic conditions.

Answer 33

strong: cannot

Question 34

In a concerted elimination reaction, which of the following are combined into one concerted step?

Answer 34

loss of leaving group and proton transfer

Question 35

Which of the following substrates will undergo substitution ONLY through a SN1 mechanism?

Answer 35

Tertiary substrate

Question 36

DBU functions as a

Answer 36

base only.

Question 37

In a SN2 substitution reaction, when can a rearrangement step occur?

Answer 37

Rearrangement steps cannot occur ever during a SN2 substitution reaction

Question 38

Only the rate of an SN2 reaction (not the rate of SN1 reaction) is dependent on the concentration of the nucleophile.

Answer 38

true

Question 39

Polarizability is directly related to the

Answer 39

size of the atom

Question 40

Generally, SN2 reactions cannot be performed in _________ solvents.

Answer 40

non polar