Organic Chemistry Ii (Test 1)

Front 1

what is the energy source in NMR?

Back 1

radio waves

Front 2

what are the requirements for a nucleus to give rise to NMR?

Back 2

a nucleus MUST have either an odd atomic number or an odd mass number

Front 3

if a nucleus aligns in the same direction as the external magnetic field is a higher or lower energy state assumed?

Back 3

lower

Front 4

if a nucleus aligns in the opposite direction as the external magnetic field is a higher or lower energy state assumed?

Back 4

higher

Front 5

when is a nucleus in resonance?

Back 5

when it absorbs RF radiation and "spin flips" to a higher energy state

Front 6

what two variables characterize NMR?

Back 6

-an applied magnetic feild (B sub 0)
-the frequency (v) of radiation used/needed for resonance

Front 7

what relationship do the frequency needed for resonance and the applied magnetic field have?

Back 7

proportional

Front 8

the _______ the magnetic field, the ________ the energy difference between the two nuclear spin states, and the _______ the v needed for resonance

Back 8

the stronger the magnetic field, the larger the energy difference between the two nuclear spin states, and the higher the v (frequency) needed for resonance

Front 9

do all protons absorb at the same frequency?

Back 9

no, protons in different environments absorb at slightly different frequencies, making them distinguishable my NMR

Front 10

what determines the frequency at which a particular proton absorbs?

Back 10

the proton's electronic environment

Front 11

what does an NMR plot?

Back 11

intensity of a peak against chemical shift

Front 12

in what direction is increasing chemical shift plotted?

Back 12

right to left

Front 13

what direction do 'upfield' and 'down-field' refer to respectively?

Back 13

upfield = right
down-field = left

Front 14

the number of NMR signals equals what?

Back 14

the number of different types of protons in a compound.

Front 15

protons in different environments give the same or different NMR signals?

Back 15

different (different environment, different signal)

Front 16

do equivalent protons give same or different NMR signals?

Back 16

same

Front 17

what's the most important thing to remember when determining number of signals for alkenes or cyloalkanes?

Back 17

they have restricted bond rotation!

Front 18

for two protons to be equivalent in a double bond or ring what must be true?

Back 18

they must both be cis (or trans) to the SAME groups (pg.498)

Front 19

where a particular proton absorbs depends on what?

Back 19

it's electronic environment

Front 20

the small magnetic field created by electrons around any given nucleus goes in the same or opposite direction of the applied magnetic field?

Back 20

opposite

Front 21

the inherent small magnetic field that opposes the applied magnetic field is said to do what?

Back 21

"shield" the nucleus from the applied field (B sub o)

Front 22

what direction does shielding shift an absorption?

Back 22

upfield (to the right)

Front 23

does a less shielded nucleus "feel" more or less of the applied magnetic field?

Back 23

it feels more of the applied magnetic field...and is said to be "deshielded"

Front 24

does a deshielded nucleus feel more or less of the applied magnetic field?

Back 24

more

Front 25

what is the result of a deshielded nucleus experiencing a higher magnetic field?

Back 25

it needs a higher frequency to achieve resonance.

Front 26

in which direction is higher frequency?

Back 26

to the left, toward higher chemical shift (they're proportional-remember?)

Front 27

what direction does deshielding shift an absorption?

Back 27

downfield ( to the left= to higher chemical shift= to higher frequency)

Front 28

in what direction do protons that are near electronegative elements absorb?

Back 28

downfield..because they are deshielded!

Front 29

decreased electron density _____ a nucleus and an absorption moves _______.

Back 29

decreased electron density deshields a nuclus and an absorption moves downfield.

Front 30

does the chemical shift value of C-H decrease or increase with increasing alkyl substitution?

Back 30

increase

Front 31

what's TMS used for?

Back 31

TMS is a denatured solvent used as an internal standard in NMR

Front 32

what is the area under an NMR signal proportional to?

Back 32

the number of absorbing protons

Front 33

how do you calculate the number of protons giving rise to each signal?

Back 33

1)add up total number of integration units and divide by the number of protons in the formula
2) individually divide each integration number by the number achieved by sum divided by protons in step 1 (pg. 506)

Front 34

what order do sp3, sp2 and sp appear in an NMR?

Back 34

sp3 is furthest right (upfield) then sp in the middle then sp2 is furthest downfield (left)

Front 35

if, on a H-NMR spectrum there is are nine SP3 furthest upfield, what is understood?

Back 35

it represents a tert-butyl group!

Front 36

does chemical shift increase/decrease with increasing chemical shift?

Back 36

increase

Front 37

when does spin-spin splitting occur?

Back 37

only between nonequivalent protons on the same or adjacent carbons.

Front 38

one adjacent H splits an NMR signal into what?

Back 38

a doublet (n+1)

Front 39

two adjacent H's splits an NMR signal into what?

Back 39

a triplet (n+1)

Front 40

when two protons split each others NMR signal, they are said to be what?

Back 40

coupled

Front 41

do equivalent protons split each other?

Back 41

noo

Front 42

splitting is not generally observed between protons separated by more than ____ sigma bonds

Back 42

3

Front 43

what are the two steps in predicting splitting?

Back 43

1) determine if two protons are equivalent or different
2) determine if two nonequivalent protons are close enough to split each others signals

Front 44

do OH or NH split NMR signals of adjacent protons?

Back 44

no

Front 45

are OH or NH protons split by other adjacent protons?

Back 45

no

Front 46

how does the NMR spec. handle cyclohexane chair formations?

Back 46

the chair flip happens so rapidly that the NMR takes an average formation and uses that in it's spectrum

Front 47

how many different types of protons does a monosubstituted benzene ring have?

Back 47

3

Front 48

what is the scale of C-NMR?

Back 48

200-0

Front 49

what is the approximate scale or H-NMR?

Back 49

about 10-0

Front 50

what is true of every peak in a C-NMR spec?

Back 50

all signals are singlets because no splitting occurs due to the low abundance of carbon 13

Front 51

in contrast to H-NMR, what is true about the peak intensity of C-NMR?

Back 51

in C-NMR peak intensity is not proportional to the number of absorbing carbons

Front 52

are C-NMR signals integrated?

Back 52

NO, only H-NMR signals are

Front 53

what occurs during oxidation??

Back 53

increase in number of C-O bonds
decrease in number of C-H bonds

Front 54

what occurs during reduction??

Back 54

increase in number of C-H bonds
decrease in number of C-O bonds

Front 55

what's the most reduced form of carbon?

Back 55

CH4

Front 56

what's the most oxidized form of carbon?

Back 56

O=C=O

Front 57

what are the three main types of reducing agents?

Back 57

1) molecular H2
2) Na in NH3
3) metal hydride (NaBH4 or LiAlH4)

Front 58

what does reduction of an alkene form?

Back 58

an alkane by the addition of H2

Front 59

the addition of H2 only occurs in the presence of a metal catalyst and thus the reaction is called what?

Back 59

catalytic hydrogenation

Front 60

in what fashion does H2 add?

Back 60

syn!

Front 61

what does oxidation result in?

Back 61

increse in C-O bonds
decrease in C-H bonds

Front 62

what does reduction result in?

Back 62

increase in C-H bonds
decrease in C-O bonds

Front 63

the conversion of an alkyne to an alkene and an alkene to an alkane are examples of what?

Back 63

reduction! because each process adds two new C-H bonds to the starting material.

Front 64

what is the simplest reducing agent?

Back 64

molecular H2 ... carried out in the presence of a metal catalyst

Front 65

what occurs during hydrogenation?

Back 65

the weak pi bond in broken and h2 is added (pg. 429)

Front 66

when type of hyrdrogenation is said to be carried out when the reaction occurs in the presence of a metal catalyst?

Back 66

catalytic hydrogenation

Front 67

what metal catalyst are usually used in catalytic hydrogenation?

Back 67

Pd, Pt, Ni

Front 68

in catalytic hydrogenation in what fashion do the 2 H's add?

Back 68

syn addition

Front 69

by what process are alkenes reduced to alkanes?

Back 69

catalytic hydrogenation

Front 70

what is catalytic hydrogenation?

Back 70

the additions of hydrogens to double or triple bonds in the presence of a metal catalyst. (Pd, Pt, Ni) in powder form= greater surface area

Front 71

is catalytic hydrogenation syn or anti addition?

Back 71

syn

Front 72

is hydrogenation exothermic or endothermic?

Back 72

exothermic

Front 73

what is delta H for hydrogenation called?

Back 73

heat of hydrogenation

Front 74

what can delta H (heat of hydrogenation) be used to measure?

Back 74

stability of different alkenes when they have the same hydrogenated products

Front 75

are cis or trans alkenes more stable after undergoing catalytic hydrogenation?

Back 75

trans.. because the heat of hydrogenation is less* meaning less heat is released, making the alkene more stable.

Front 76

when cis and trans alkenes both undergo catalytic hydrogenation under the same conditions, which will be more stable?

Back 76

trans, even though the products are the same!

Front 77

cis and trans alkenes both undergo catalytic hydrogenation under the same conditions.... are the the products the same or different?

Back 77

the same

Front 78

more stable alkene has a large or small delta H (heat of hydrogenation) ??

Back 78

more stable alkene, small delta H

Front 79

does a less stable alkene have a smaller or later delta H?

Back 79

larger delta h, less stable

Front 80

a more stable alkene has the ______ heat of hydrogenation.

Back 80

smaller

Front 81

the less stable alkene has the _____ heat of hydrogenation.

Back 81

larger

Front 82

when can you use heat of hydrogenation data to evaluate relative stability of starting materials?

Back 82

only when the hydrogenation products are the SAME

Front 83

the mechanism by which hydrogenation occurs implies what two facts?

Back 83

1) rapid, sequential addition of H2 occurs from the side of the alkene complexed to the metal surface
2) less crowded double bonds complex more readily to the catalyst surface, resulting in faster rxn

Front 84

do less crowded or more crowded alkenes have a faster rate of hydrogenation ?

Back 84

less crowded! the fewer R groups, the faster the rxn. the more R groups, the slower the reaction

Front 85

what does the degrees of unsaturation tell you about a molecule?

Back 85

the total number of rings and bonds in the molecule

Front 86

what are the steps and the formula for calculating degrees of unsaturation?

Back 86

-CnH2n+2 tells maximum number of hydrogens
- you then substract actual from the maximum
- then divide that by 2

Front 87

the number of degrees of unsaturation that remain in the product AFTER H2 addition equals what?

Back 87

the number of rings in the starting material

Front 88

the number of degrees of unsaturation that react with H2 equals what?

Back 88

the number of pi bonds

Front 89

what other double bonded functional group reacts with h2 and a metal catalyst??

Back 89

compounds with carbonyl groups

Front 90

what are aldehydes reduced to?

Back 90

primary alcohols

Front 91

what are ketones reduced to?

Back 91

secondary alcohols

Front 92

what occurs during reduction of an alkyne?

Back 92

h2 is added to one or both of the pi bonds

Front 93

what is formed when 2 eq. of h2 are reacted with an alkyne ?

Back 93

an alkane

Front 94

what is formed when 1 eq. of h2 is reacted with an alkyne? (and adds in a syn fashion)

Back 94

a cis alkene

Front 95

what is formed when 1 eq. of h2 is reacted with an alkyne? (and adds in a anti fashion)

Back 95

a trans alkene

Front 96

when an alkyne is treated with 2 eq. of h2 and a Pd catalyst, what 2 things happen?

Back 96

reduction of both pi bonds occurs 1) syn addition of one equivalent of h2 forms a cis alkene
2) a second eq. of h2 is then added to form and alkane

Front 97

when an alkyne is treated with 2 eq. of h2 and a Pd catalyst how many new c-h bonds are formed?

Back 97

4

Front 98

are internal alkynes more or less stable than terminal alkynes?

Back 98

more stable

Front 99

when and why is a lindlar catalyst used?

Back 99

the lindlar catalyst is used when reducing an alkyne to CIS alkene because regular pd is to active to allow the reaction to stop after just 1 eq of h2 --> it will go all the way to an alkane if just used Pd

Front 100

what is a lindlar catalyst?

Back 100

Pd absorbed onto CaCO3 + lead acetate + quinoline

Front 101

does use of Lindlar catalyst result in cis or trans alkenes?

Back 101

cis!

Front 102

Pd will always reduce alkynes and alkenes to what?

Back 102

alkanes

Front 103

Lindlar catalyst will reduce what to what?

Back 103

alkynes to cis alkenes ONLY!

Front 104

what catalyst is used in the reduction of an alkyne to a trans alkene?

Back 104

Na + NH3

Front 105

what catalyst is used in the reduction of an alkyne to a cis alkene?

Back 105

Lindlar catalyst: Pd/CaCO3 + lead acetate + quinoline

Front 106

can catalytic hydrogenation be used to prepare trans alkenes from alkynes ?

Back 106

no

Front 107

can catalytic hydrogenation be used to prepare cis alkenes from alkynes?

Back 107

yes

Front 108

when reducing an alkyne to a trans alkene, how are the elements of H2 added?

Back 108

in an anti fashion, forming a trans-alkene

Front 109

what is the use of NH3 + Na in reduction of a alkyne to a trans alkene called?

Back 109

dissolving metal reduction AKA birch reduction

Front 110

alkyl halides and epoxides contain ______ that makes them react with strong nucleophiles and undergo reduction via _______ reagents.

Back 110

1) polar C-X bonds
2) metal hydride

Front 111

when epoxides are reduced using metal hydride reagents, what is the product?

Back 111

alcohol (epoxide rings are opened to form alcohols

Front 112

when alkyl halides are reduced using metal hydride reagents what is the product?

Back 112

alkane - with X as the leaving group

Front 113

the reduction of the polar C-X bonds found in epoxides and alkyl halides is an example of what?

Back 113

nucleophilic substitution - SN2 (where H- is the strong nucleophile)

Front 114

because the reduction of epoxides and alkyl halides with metal hydride reagents is a SN2 reaction, what is true about the primary and unhindered alkyl halides?

Back 114

they react FASTEST! unhindered and primary alkyl halides react fastest via SN2 mechanism (are more easily reduced)

Front 115

in umsymmetrical epoxides, the nucleophillic attack of H- occurs at the more or less substituted carbon?

Back 115

less**

Front 116

in reduction of epoxides and alkyl halides, what is the metal hydride reagent most typically used?

Back 116

LiAlH4

Front 117

what is epoxidation?

Back 117

the addition of a single oxygen atom to an alkene to form an epoxide

Front 118

with what oxidizing agent is epoxidation usually carried out?

Back 118

peroxyacid ..but also mcpba

Front 119

what three oxidative reactions alkenes undergo?

Back 119

1)epoxidation
2)dihydroxylation
3)double bond cleavage (oxidative cleavage)

Front 120

what oxidative reaction do alkynes undergo?

Back 120

1)triple bond cleavage (oxidative cleavage)

Front 121

a cis alkene gives an epoxide with ___ substituents. a trans alkene gives an epoxide with ____ substituents.

Back 121

cis alkene= cis epoxide
trans alkene= trans epoxide

Front 122

are epoxidation reactions stereospecific?

Back 122

yes, because cis and trans alkenes yeild different stereoisomers as products. position of substituents is retained in epoxidation rxns

Front 123

cis-2-butene treated with mcpba = ? (epoxidation rxn)

Back 123

achiral meso compound with 2 stereogenic centers

(in which the oxygen can be added either to the top of the plane or below the plane)

Front 124

trans-2-butene treated with mcpba =? (epoxidation)

Back 124

pair of enantiomers (racemic mixture )

Front 125

who is responsible for retrosynthetic analysis?

Back 125

EJ Corey

Front 126

what is retrosynthetic analysis?

Back 126

working backwards...

Front 127

what is dihydoxylation?

Back 127

the addition of two hydroxy groups to a double bond forming a 1,2-diol or gycol. (can be syn or anti addition depending on reagent used)

Front 128

when does syn-dihydroxylation occur?

Back 128

when an alkene is treated with either:

1.) KMnO4 + H20 + OH-
2.) [1]OsO4 + [2] NaHSO3 + H20

Front 129

what is NMO?

Back 129

N-methyl morpholine N-oxide: used to "dilute" OsO4 because OsO4 is expensive and toxic (used in syn-dihydroxylation reactions!)

Front 130

what is the disadvantage of using KMn04 in syn-dihydroxylation reactions?

Back 130

it's use is limited by its insolubility in organic solvents.

Front 131

what is the disadvantage of using OsO4 in sny-dihydroxylation reactions?

Back 131

it's toxic and expensive - so NMO is added to it

Front 132

what is the "cycle" that occurs with the use of OsO4 in syn-dihydroxylation?

Back 132

one of the products formed (OsO3) can then be used for dihydroxylation once again, and the cycle continues

Front 133

which dihydroxylation occurs in two steps? (syn or anti)

Back 133

anti

Front 134

what are the 2 steps in which an alkene is converted to a diol via anti-dihydroxylation?

Back 134

alkene--->epoxide--->diol

Front 135

in anti dihydroxylation what is used to go from alkene to epoxide?

Back 135

mcpba

Front 136

what is RCO3H?

Back 136

peroxyacid!!!!

Front 137

what are the reagents primarily used in anti dihydroxylation?

Back 137

[1] peroxyacid
[2] hydroxide

Front 138

in general...what type of reaction is the opening of an epoxide?

Back 138

sn2 reaction --in which the least hindered C is "attacked"

Front 139

when a symmetrical epoxide is treated with peroxyacid and hydroxide what happens and what is the end result?

Back 139

a sym. epoxide has equal chance of being attacked at either carbon, therefore a pair of enantiomers is the final product

Front 140

anti-dihydroxylation gives what as prodcut?

Back 140

enantiomers

Front 141

dihydroxylation with peroxyacid gives what?

Back 141

ANTI addition. TRANS products

Front 142

dihydroxylation with KMnO4 or OsO4 gives what?

Back 142

SYN addition. CIS products

Front 143

what is oxidative cleavage of an alkene?

Back 143

both the sigma and the pi bond of the alkene are broken to form two carbonyl groups. depending on the number of R groups bonded to the double bond, you either get KETONES or ALDEHYDES.

Front 144

what are always the products of oxidative cleavage of alkenes?

Back 144

ketones and/or aldehydes

Front 145

wwhat's the easiest way to draw the products of oxidative cleavage in alkenes?

Back 145

split the double bond down the middle and add an 'O' to each end of the break

Front 146

what reagent is commonly used in oxidative cleavage??

Back 146

[1]ozone (O3)
[2] Zn, H20 ///or/// CH3SCH3

Front 147

what occurs during oxidatitive cleavage?

Back 147

both pi and sigma bonds are broken and two carbonyl groups are formed= either ketones or aldehydes

Front 148

what are always the products of oxidative cleavage of alkenes?

Back 148

ketone
aldehyde

Front 149

what is typically used in oxidative cleavage of alkenes?

Back 149

ozone
Zn, h20 (or CH3SCH3)

Front 150

what are the steps in drawing the products of any oxidative cleavage?

Back 150

break the double bonds, then add 'O's at the breaks

Front 151

what are internal alkynes oxidized to (oxidative cleavage) ?

Back 151

carboxylic acids

Front 152

what are terminal alkynes oxidized to (oxidative cleavage) ?

Back 152

a carboxylic acid and CO2

Front 153

what is commonly used in the oxidative cleavage of alkynes?

Back 153

ozone followed by h20

Front 154

in hydrogenation (reduction) reactions, what is the relationship between number of R groups and rate of hydrogenation?

Back 154

fewer R groups, faster RXN
more R groups, slower RXN

Front 155

more stable alkene= what in terms of delta H?

Back 155

more stable alkene = smaller heat of hydrogenation

Front 156

less stable alkene = what in terms of delta H?

Back 156

less stable alkene = higher heat of hydrogenation

Front 157

what are primary alcohols oxidized to?

Back 157

aldehydes or carboxylic acid

Front 158

what are secondary alcohols oxidized to?

Back 158

ketones

Front 159

what are tertiary alcohols oxidized to?

Back 159

they do not react!

Front 160

in oxidation of alcohols, what is considered a mild oxidizing agent?

Back 160

PCC [[in CH2Cl2]]

Front 161

in oxidation of alcohols what is considered a strong oxidizing agent?

Back 161

CrO3, Na2CrO7, K2Cr2O7 [[in h20 and H2SO4]]

Front 162

in oxidation of alcohols, what is the product when alcohol is treated with PCC?

Back 162

pcc is mild so you get aldehyde

Front 163

what kind of oxidizing agent is need to oxidize secondary alcohols?

Back 163

either a strong or weak (pcc) will oxidize 2* alcohols... into what you ask???????

a ketone

Front 164

2* alcohols are oxidized to what?

Back 164

ketones - with either strong or weak [o] agent

Front 165

when a weak [o] agent is used, what are 1* ROH oxidized to?

Back 165

aldehydes

Front 166

when strong [o] agent is used, what are 1* ROH oxidized to?

Back 166

carboxylic acid