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CHEM 1220 > Ch. 21: Organic Chemistry II: Reactions > Flashcards

Ch. 21: Organic Chemistry II: Reactions Flashcards

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1
Q

define synthesis

A

the process of making compounds in one or more steps

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2
Q

define resonance effect

A

the stabilization of a chemical species through pi delocalization

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3
Q

define inductive effect

A

the through-bond donation or withdrawal of electron density

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4
Q

define carbanion

A

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

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5
Q

define hydrogenation

A

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

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6
Q

define interconversion

A

functional group transformation

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7
Q

define nucleophile

A

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

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8
Q

define leaving group

A

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

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9
Q

define substrate

A

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

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10
Q

define electrophile

A

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

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11
Q

define carbocation

A

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

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12
Q

define racemization

A

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

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13
Q

define nucleophilicity

A

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

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14
Q

define 1,2 elimination

A

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

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15
Q

define dehydration

A

the elimination of water from an alcohol to yield an alkene

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16
Q

define dehalogenation

A

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

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17
Q

define Zaitsev’s rule

A

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

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18
Q

define oxonium ion

A

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

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19
Q

what is Ka

A

a measure of acid strength

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20
Q

as electron affinity increases acidity ____

A

increases

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21
Q

the higher the pKa the ___ acidic the chemical is

A

less

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22
Q

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

A

greater

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23
Q

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

A

bond dipole

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24
Q

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

A

yes

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25
Q

if the conjugate base is resonance stabilized the acid becomes ____

A

stronger

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26
Q

why are the pKa values of alkenes very high?

A

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

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27
Q

what is a mechanism?

A

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

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28
Q

acid=…?

A

electron pair acceptor

29
Q

base=….?

A

electro pair donor

30
Q

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

A

strongest

31
Q

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

A

higher

32
Q

Oxidation involves the ____ of electrons

A

loss

33
Q

Reduction involves the ____ of electrons

A

gain

34
Q

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

A

(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

35
Q

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

A

oxidation state

36
Q

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

A

hydrogen

37
Q

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

A

it means a gain of two electrons

38
Q

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

A

reduced

39
Q

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

A

oxidzed

40
Q

hydrogenantion and reduction are ____ terms

A

equivalent

41
Q

primary alcohols are oxidized to ____

A

aldehydes

42
Q

secondary alcohols are oxidized to ____

A

ketones

43
Q

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

A

SN1 and SN2

44
Q

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

A

stabilized

45
Q

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

A

is not

46
Q

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

A

is

47
Q

racemization occurs in a SN1 reaction because…?

A

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

48
Q

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

A

the carbon atom switches fromR to S configuration or vice versa

49
Q

a good nucleophile will cause an SN2 reaction to occur ____

A

quicker

50
Q

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

A

no change

51
Q

the best leaving groups are…?

A

the conjugate bases of strong acids

52
Q

what is the citerion for a good leaving group?

A

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

53
Q

for Sn1 reactions what greatly affects the rate of the reaction

A

the stability of the carbocation reaction intermediate

54
Q

what does the stability of a carbocation depend on?

A

the number of alkyl groups bonded to it

55
Q

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

A

increasing

56
Q

in Sn2 reactions, the rate is affected by ____ ___

A

steric hinderance

57
Q

methyl and primary substrates ___ undergo Sn1 substitutions

A

never

58
Q

tertiary substrates never ____ undergo Sn2 substitution reactions

A

never

59
Q

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

A

repulsion

60
Q

dehydration reactions occur in the presence of…?

A

a strong acid and heat

61
Q

dehalogenantion reactions often require the prescence of…?

A

a strong base and heat

62
Q

why do many elimination reactions give mixtures of products?

A

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

63
Q

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

A

E1

64
Q

E2 mechanisms generally require a ___ base

A

strong

65
Q

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

A

primary

primary

66
Q

what carbons centers can E2 eliminations occur on?

A

primary, secondary and tertiary

67
Q

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

A

nucleophiles

68
Q

as a general rule a strong bases favours ___ over ___

A

elimination over substitution

CHEM 1220 (4 decks)

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