Exam 3

Question 1

What reaction type do strong nucleophiles favor?

Answer 1

SN2 reactions

Question 2

What reaction type do weak nucleophiles favor?

Answer 2

SN1 reactions

Question 3

How does charge correlate to nucleophile strength?

Answer 3

a more negative charge = stronger nucleophile

Question 4

What is the trend of nucleophile strength on the periodic table?

Answer 4

increases towards carbon

Question 5

What reaction type do strong bases favor?

Answer 5

E2

Question 6

What reaction type do weak bases favor?

Answer 6

E1

Question 7

How to determine a weak base?

Answer 7

it is the conjugate base of a strong acid; add an H+ proton and determine acid strength

Question 8

What reaction types does a high concentration of attacking species favor?

Answer 8

SN2 and E2 (assume high conc. unless specified)

Question 9

What reaction types does a diluted (dil.) concentration of attacking species favor?

Answer 9

E1 and SN1

Question 10

What kind of base or acid do leaving groups tend to be?

Answer 10

weaker bases

Question 11

What is TsO-?

Answer 11

one of the best leaving groups

Question 12

What is MsO-?

Answer 12

one of the best leaving groups

Question 13

What is TfO-?

Answer 13

one of the best leaving groups

Question 14

What is HSO4-?

Answer 14

one of the best leaving groups

Question 15

What reaction types do good leaving groups favor?

Answer 15

all of them

Question 16

What reaction types do poor leaving groups favor?

Answer 16

SN2 and E2 reactions

Question 17

What reaction types does heat (∆) favor?

Answer 17

elimination (E1 and E2)

Question 18

What hybridization must a carbon have for a SN1, SN2, E1, or E2 reactions to occur?

Answer 18

sp3

Question 19

Why does sp3 hybridized carbon allow substitution and elimination reactions to occur?

Answer 19

because it has the weakest bond strength and electronegativity making it easy for the LG to leave

Question 20

What reaction types does a primary carbon bonded to the leaving group favor?

Answer 20

SN2 and E2

Question 21

What reaction types does a secondary carbon bonded to the leaving group favor?

Answer 21

all of them

Question 22

What reaction type does a tertiary carbon bonded to the leaving group prevent?

Answer 22

SN2

Question 23

What is the only reaction type a methyl carbon bonded to the leaving group allows?

Answer 23

SN2

Question 24

What type of solvent is DmSO?

Answer 24

Aprotic

Question 25

What type of solvent is DMF?

Answer 25

Aprotic

Question 26

What type of solvent is THF?

Answer 26

Aprotic

Question 27

What type of solvent is acetone?

Answer 27

Aprotic

Question 28

What reaction types do aprotic solvents favor?

Answer 28

SN2 and E2 reactions

Question 29

Why do aprotic solvents favor E2 and SN2 reactions?

Answer 29

because they solvate weakly so they don't block the nucleophile from attacking the molecule

Question 30

What type of solvents have N-H or O-H bonds?

Answer 30

Protic solvents

Question 31

Why do protic solvents favor SN1 and E1 reactions?

Answer 31

because they strongly solvate the nucleophile, making it less reactive, and strongly solvate the LG making it more reaction

Question 32

Which regiosomer do elimination reactions favor according to Zaitzev's rule?

Answer 32

the major regiosomer is the one with the less substituted alkene (pg. 11 of Carra notes)

Question 33

What is a regioisomer?

Answer 33

isomers with the same functional groups attached at different positions of the molecular backbone

Question 34

Do low concentration reaction favor intramolecular interactions or intermolecular interactions?

Answer 34

intramolecular (within one molecule)

Question 35

Do high concentration reaction favor intramolecular interactions or intermolecular interactions?

Answer 35

intermolecular (between multiple molecules)

Question 36

What are important rules/limitations of using PBr3 and PCl3 to convert alcohol into alkyl halides?

Answer 36

the carbon must be sp2 hybridized it cannot be a tertiary carbon it is a stereospecific reaction

Question 37

Which type of molecule (1st step) facilitates the attachment of an alkyl to the least substituted alpha carbon during alkylation of an alpha carbon?

Answer 37

Strong bulky bases

Question 38

What kind of atom must be attached to an alkyl (2nd step) for alkylation of an alpha carbon to occur?

Answer 38

a halogen (Br)

Question 39

Why do strong bulky bases cause alkylation on the least substituted alpha carbon of a molecule?

Answer 39

the de-protonation of less the sterically hindered H is irreversible

Question 40

Which type of molecule (1st step) facilitates the attachment of an alkyl to the most substituted alpha carbon during alkylation of an alpha carbon?

Answer 40

bulky bases weaker than LDA

Question 41

Why do bulky bases weaker than LDA alkylation on the most substituted alpha carbon of the molecule?

Answer 41

because the deprotonation of the less sterically hindered H is reversible, so the more stable enolate is able to form

Question 42

What is a enolate?

Answer 42

a deprotonated (has a lone pair and (-) charge) oxyen-carbon double bond in a molecule

Question 43

What is a therodynamic enolate?

Answer 43

a more stable enolate

Question 44

What enolate does room temp favor?

Answer 44

theromdynamic enolate

Question 45

What is the first step of halogenation of an alpha carbon?

Answer 45

to deprotonate the alpha carbon using a base from the solvent

Question 46

What is the second step of halogenation of an alpha carbon?

Answer 46

the lone pair of the enolate attacks the partial positive of the halogen pair

Question 47

How does halogenation of an alpha carbon affect stereochemistry?

Answer 47

a mixture of 2 stereoisomers is created because the during the sp2 hybridized phase of the enolate, the molecule becomes planar

Question 48

When does polyhalogenation occur?

Answer 48

when more than one H exists on the alpha carbon for the halogens to replace

Question 49

Why would polyhalogenation not occur even if more than one H is on the alpha carbon?

Answer 49

acidic conditions

Question 49

What product forms when a akylhalide (R-X) is reacted with a alkoxide ((-)OR')

Answer 49

R - O - R' (an ether)

Question 50

What is this reaction called: R-X → R - O - R' (→ = (-)OR')

Answer 50

Williamson Ether Synthesis

Question 51

What type of reaction occurs during Williamson Ether Synthesis?

Answer 51

SN2

Question 52

What step must first occur before an alcohol can undergo William Ether Synthesis?

Answer 52

a base must deprotonate it

Question 53

What is limitation/rule of William Ether Synthesis?

Answer 53

it cannot occur at tertiary alkyl halides 3* carbons can not perform SN2 reactions

Question 54

Does an intermolecular/intramoleculer reaction occur if a halide ion and alkoxide are on the same molecule?

Answer 54

an intramolecular William Ether Synthesis

Question 55

What is an alpha carbon?

Answer 55

a carbon that is one away from a Ketone or Aldehyde (carbon-oxygen double bond)