Ch. 21: Organic Chemistry II: Reactions

Question 1

define synthesis

Answer 1

the process of making compounds in one or more steps

Question 2

define resonance effect

Answer 2

the stabilization of a chemical species through pi delocalization

Question 3

define inductive effect

Answer 3

the through-bond donation or withdrawal of electron density

Question 4

define carbanion

Answer 4

a chemical species that contains a carbon atom with a formal negative charge

Question 5

define hydrogenation

Answer 5

the catalyzed addition of hydrogen to alkene double bonds to make single bonds

Question 6

define interconversion

Answer 6

functional group transformation

Question 7

define nucleophile

Answer 7

a chemical species that can donate electrons to an electrophilic site on another molecule, leading to bond formation

Question 8

define leaving group

Answer 8

the group that is removed from a substrate in a substitution reaction

Question 9

define substrate

Answer 9

the reactant molecule in a biochemical reaction that binds to an enzyme at the active site

Question 10

define electrophile

Answer 10

a molecule that contains an atom with a positive charge which can accept electrons from another molecule, such as a nucleophile

Question 11

define carbocation

Answer 11

a chemical species that contains a carbon atom with a formal positive charge

Question 12

define racemization

Answer 12

the loss of stereochemical purity in a chemical reaction, such as in SN1 substitutions

Question 13

define nucleophilicity

Answer 13

a measure of the effectiveness, or strength, of a nucleophile

Question 14

define 1,2 elimination

Answer 14

the loss of atoms or groups, bonded to adjacent carbon atoms in alkane, yielding an alkene

Question 15

define dehydration

Answer 15

the elimination of water from an alcohol to yield an alkene

Question 16

define dehalogenation

Answer 16

the elimination of HX from an alkyl halide to yield an alkene

Question 17

define Zaitsev’s rule

Answer 17

when isomeric alkenes are produced in an elimination reaction, the major product is usually the most substituted alkene

Question 18

define oxonium ion

Answer 18

a chemical species in which an oxygen atom carries a formal positive charge

Question 19

what is Ka

Answer 19

a measure of acid strength

Question 20

as electron affinity increases acidity ____

Answer 20

increases

Question 21

the higher the pKa the ___ acidic the chemical is

Answer 21

less

Question 22

a chemical effected by induction has a ____ acidity than a very similar chemical that is not effected by induction

Answer 22

greater

Question 23

the inductive effect is a result of ____ ____ that polarize other bonds in the atom

Answer 23

bond dipole

Question 24

is it possible for the inductive effect to effect bonds that are many bonds away from the electronegative atom and its resulting dipole?

Answer 24

yes

Question 25

if the conjugate base is resonance stabilized the acid becomes ____

Answer 25

stronger

Question 26

why are the pKa values of alkenes very high?

Answer 26

because the charge is completely localized on a carbon atom and there is no additional stabilization of the charge

Question 27

what is a mechanism?

Answer 27

an attempt to represent a reaction at a molecular level, in a step-by-step manner

Question 28

acid=...?

Answer 28

electron pair acceptor

Question 29

base=....?

Answer 29

electro pair donor

Question 30

the conjugate acid with the highest pKa results in the ____ base

Answer 30

strongest

Question 31

to react with an acid, a base must have a conjugate acid that has a pKa ___ than that of the reactant acid

Answer 31

higher

Question 32

Oxidation involves the ____ of electrons

Answer 32

loss

Question 33

Reduction involves the ____ of electrons

Answer 33

gain

Question 34

what are the three rules for determining the oxidation state of an atom?

Answer 34

(1) each bond to an atom that is LESS electronegative is counted as -1 toward the oxidation state (2) each bond to an atom that is MORE electronegative is counted as +1 toward the oxidation state (3) bonds to the same type of atom are not counted

Question 35

to determine wether electrons have been lost or gained we examine the changes in ____ _____

Answer 35

oxidation state

Question 36

the reduction of an organic molecule usually involves the addition of a _____

Answer 36

hydrogen

Question 37

if the change in oxidation state is -2 what does this mean about the loss or gain of electrons?

Answer 37

it means a gain of two electrons

Question 38

if the change in oxidation state is negative the atom has be ____

Answer 38

reduced

Question 39

if the change in oxidation state is positive the atom has be ____

Answer 39

oxidzed

Question 40

hydrogenantion and reduction are ____ terms

Answer 40

equivalent

Question 41

primary alcohols are oxidized to ____

Answer 41

aldehydes

Question 42

secondary alcohols are oxidized to ____

Answer 42

ketones

Question 43

what are the two principle mechanisms for nucleophilic substitutions at saturated carbons?

Answer 43

SN1 and SN2

Question 44

the formation of the carbocation intermediate in a SN1 reaction is most likely to occur if the carbocation is _____ by the structure of the substrate

Answer 44

stabilized

Question 45

the second step in the overall SN1 reaction ____ (is/is not) the rate determining step

Answer 45

is not

Question 46

the first step in the overall SN1 reaction ____ (is/is not) the rate determining step

Answer 46

is

Question 47

racemization occurs in a SN1 reaction because...?

Answer 47

if the substrate is originally a chiral center it will become a trigonal planar molecule and then when then the nucleophile attacks it could become either R or S configuration

Question 48

what is the effect of the inversion that occurs during and SN2 reaction/

Answer 48

the carbon atom switches fromR to S configuration or vice versa

Question 49

a good nucleophile will cause an SN2 reaction to occur ____

Answer 49

quicker

Question 50

a good nucleophile causes ____ in the rate of a SN1 reaction

Answer 50

no change

Question 51

the best leaving groups are...?

Answer 51

the conjugate bases of strong acids

Question 52

what is the citerion for a good leaving group?

Answer 52

the leaving group must develop and accept a negative charge and the corresponding ANION being very STABLE

Question 53

for Sn1 reactions what greatly affects the rate of the reaction

Answer 53

the stability of the carbocation reaction intermediate

Question 54

what does the stability of a carbocation depend on?

Answer 54

the number of alkyl groups bonded to it

Question 55

stability of a carbocation increases with ____ number of alkyl groups bonded to it

Answer 55

increasing

Question 56

in Sn2 reactions, the rate is affected by ____ ___

Answer 56

steric hinderance

Question 57

methyl and primary substrates ___ undergo Sn1 substitutions

Answer 57

never

Question 58

tertiary substrates never ____ undergo Sn2 substitution reactions

Answer 58

never

Question 59

steric hinderance is a result of the ____ between the alkyl groups on the substrate and the nucleophile

Answer 59

repulsion

Question 60

dehydration reactions occur in the presence of...?

Answer 60

a strong acid and heat

Question 61

dehalogenantion reactions often require the prescence of...?

Answer 61

a strong base and heat

Question 62

why do many elimination reactions give mixtures of products?

Answer 62

because there are often two or more elimination sites around the -X or -OH groups

Question 63

if a weak based is used an elimination reaction will likely occur via an _____ mechanism

Answer 63

E1

Question 64

E2 mechanisms generally require a ___ base

Answer 64

strong

Question 65

the E1 mechanism does not generally occur in ____ alcohols or ____ alkyl halides

Answer 65

primary | primary

Question 66

what carbons centers can E2 eliminations occur on?

Answer 66

primary, secondary and tertiary

Question 67

bases are also ____ which causes both elimination and substitution reactions to occur

Answer 67

nucleophiles

Question 68

as a general rule a strong bases favours ___ over ___

Answer 68

elimination over substitution