ochem final

Question 1

in an E1 elimination

1. the base removes a proton from the beta carbon in the first step
2. the base removes an atom from the beta carbon in the second step
3. the leaving group departs from the alpha carbon in the first step

Answer 1

3. the leaving group departs from the alpha carbon in the first step

Question 2

the stereo chemistry of the highligted carbon in the following compound is

1 r

2 s

3 neither

Answer 2

R

Question 3

which of the following reactions exhibits primary kinetic isotope effect>

1. Sn2
2. E1
3. E2

Answer 3

3 E2

Question 4

which reactions are entropically favored

1. eliminations
2. substitutions
3. additions

Answer 4

1 Eliminations

Question 5

(2S,3S) -2-amino-3-methylpentanoic acid ( the alpha amino acid L isolucine) has a specific rotation of 41* the stereoisomer (2r,3R) -2-amino-3- methylpentanoica acid has a specific rotation that

1. is -41.0*
2. is 0*
3. cannot be predicted

Answer 5

1 -41*

Question 6

which compound is the most reactive toward nuclephilic substitution

1 1,2- epoxypropane

2. 1-methoxypropane
3. propan-1-ol

Answer 6

3 propanol

Question 7

alchohols can act as

1. acid only
2. base only
3. either acid or bases

Answer 7

3 either acid or bases

Question 8

Sn1 reactions afford

1. complete retention of configuration
2. racemization or partial inversion of configuration
3. complete inversion of the configuration

Answer 8

2 racemization or partial inversion of configuration

Question 9

phenols are more acidic than alchohols due to

1. sterics
2. resonance stabilization of the corresponding conjugate base
3. increased nucleophilicity

Answer 9

2 resonance stabilization of the corresponding conjugate base

Question 10

which carbo cation is the least stable?

Answer 10

1

Question 11

which of the following compounds has the most exothemic heat of hydrogenation

1. hex-1-ene
2. trans hex-3-ene

3 (Z)-3-methylhex-3-ene

Answer 11

hex-1-ene

Question 12

2 which of the following compounds is least likely to have its molecular ion appear in its electron impact mass spectrum ?

Answer 12

1

Question 13

if a compound has a molecular formula of C8 H14 which of the following functional groups are possibly present

1. cyclic diene
2. acyclic alkyne
3. benzing ring

Answer 13

2 acyclic alkyne

Question 14

Simmons Smith cyclopropanation of 1,2disubstituted alkenes is

1. non-diastereoselective
2. partially diastereoselective
3. completely diastereoselective

Answer 14

2 completely diastereoselective

Question 15

which nucleus has a higher equilibrium population excess of its alpha spin state

1 ¹H

2. ¹³C
3. both have the same population excess

Answer 15

¹³C

Question 16

Sn2 reactions occur with

1. no sterochemical control
2. partial stereochemical control
3. complete stereochemical control

Answer 16

3 complete stereo chemical control

Sn2 reactions always occurs with complete stereochemistry control, because every time the nucleophile attacks, it always do for the opposite side of the leaving group.

Question 17

PCC oxidation of a primary alchohol affords the corresponding

1. carbocylic acid
2. aldehyde
3. ester

Answer 17

2. PCC is a great nucleophile to oxydize alcohols. Depending of the type of alcohol, it can be oxydize to ketones or aldehydes. 2nd and 3rd alcohols gets oxydized to ketones, and 1st alcohols are oxydized to aldehydes.

Question 18

Oxidation of 1-butanethiol with dilute hydrogen peroxide yields

1. 1 an alcohol
2. sulfide
3. disulfide

Answer 18

. You will get from here an alcohol.

Question 19

epoxides are reactive compounds due to

angel strain

torsional strain

steric strain

Answer 19

Angel strain

Question 20

which of the following compounds is an aromatic

Answer 20

Compound b) is aromatic basically because it’s double bonds are conjugate, and the rule 4n+2 it’s done:
4n + 2 = 10 electrons –> n = 2

Question 21

which reaction often yields product mixtures due to rearrangements

Sn1

Sn2

E2

Answer 21

Sn1

Question 22

other factors being equal a more electronegative leaving group makes an Sn2 reaction proceed

slower ‘

faster’

same rate

Answer 22

Slower

Question 23

the stereochemical configuration ofthe following diol is

Answer 23

S

Question 24

the following reaction is

Answer 24

partially enantioselective and completely diastereoselective

Question 25

which of the following reagents is the most nucleophilic

Answer 25

EtO^-Na ⁺

Question 26

Answer 26

in mass spectromety only radical cation are detected no free radicals are detected hence 3 is the answer

Question 27

which of the following reactions is stereoselective 1 HBR addition to )E) -hept-2-ene 2 reaction of osmium tetroxide and N-methylmorpholine n-oxide(NMO) with (e) hept-2-ene 3. reaction of hydrogen gas and catalitic palladium on charcoal with E)-hept-2-ene

Answer 27

HBr addition since stereoselective + when there is options for the formation of two stereo chemical components at one chiral center

Question 28

what is the maximum number of sets of ¹H NMR resonances for the follwoing alcohol ?

Answer 28

Question 29

if a compounds molecular formula is C9 H14O2 it posesses 3, 4, or 5 degrees of unsaturation

Answer 29

3

Question 30

which bond vibration is expected to have the most intense infrared absorption C-D C-Cl C-N

Answer 30

C-D

Question 31

the mass spectrum of a compound has molecular ions at 106 and 108 with relative intensity ratio of 3:1 from this information one can fairly be certain that the compound contains 1. bromine 2 chlorine 3. nitrogen

Answer 31

2 chlorine chlorine will appear 3:1 ration for M and M +2 ratio

Question 32

A CARBONYL functional group stretching absorbtion is 1 weak 2 moderate 3 strong

Answer 32

3 Strong

Question 33

the harmonic oscillator model contains a potentional energy that is 1 completely symmetrical 2. primarily symetrical but with an unsymmetrical component 3. completely unsymmetrical

Answer 33

2. primarily symetrical but with an unsymmetrical component

Question 34

which of the following species cannot be observed by mass spectrometer 1 a cation 2 radical cation 3 radical

Answer 34

1. cation

Question 35

¹³C NMR signals are less intense than ^1H Nmr signals due to: 1 larger T1 and larger Y values 2 larger T1 and smaller Y values 3. smaller T1 and smaller Y values 4 Smaller T1 and larger Y values

Answer 35

2 larger T1 and smaller Y values

Question 36

Staggered and eclipsed ethane differ in configuration consitution conformation

Answer 36

conformation '

Question 37

the most stable radical is

Answer 37

Question 38

Answer 38

2 . Sp3, Sp2 Sp

Question 39

if the concentrations of both bromoethane and sodium hydroxide are tripled the rate of the corresponding substitution reaction will be three times faster 6X faster 9Xfaster

Answer 39

6X faster the reaction is second order

Question 40

(S)-1-chlorobutan-2-ol posseses 1 four sets of chemically equivalent protons five sets seven sets

Answer 40

2 five sets of chemically equivalent protons

Question 41

in electron impact mass spectrometer the energy of the electron beam is 1 much more than the energy of a typical covalent bond 2 approximately the energy of a typical covalent bond much less than a typical covalent bond

Answer 41

1 much more than the energy of a typical covalent bond

Question 42

organic compounds containing nitrogen 1 always have an even molecular weight always have an odd MW can either have even or odd MW

Answer 42

can either have even or odd MW

Question 43

any fragmentation product observed in a mass spectrum has 1. a larger m/z value than the molecular Ion 2. a smaller m/z value than the molecular Ion 3. the same m/z value than the molecular Ion

Answer 43

2. a smaller m/z value than the molecular Ion

Question 44

which spectrometric technique can be used to determine molecular connectivity 1 IR 2. NMR 3. UV-VIS

Answer 44

NMR

Question 45

as one increases either the m₁ or m2 mass of a harmonic oscillator the reduced mass µ of the system increases decreases remains constant

Answer 45

Increases µ=m₁m₂/m₁+m₂

Question 46

the signal with the highest m/z value in a mass spectrum 1 always is the molecular ion 2 usually the molecular ion 3 never the molecular ion

Answer 46

always the molecular ion

Question 47

(2R, 5S) -5-bromohexan2-ol and (2R, 5r) -5-bromohexan2- ol are 1 diastereomers 2 enantiomers 3. refioisomers

Answer 47

1. diastereomers

Question 48

Sn2 reactions proceed with 1. racemization 2. rentention of configuration 3. inversion of configuration

Answer 48

3 inversion of configuration

Question 49

protons have different chemical shifts due to 1. spin-spin coupling 2. different local induced magnetic fields 3. different external magnetic fields

Answer 49

2. different local induced magnetic fields

Question 50

the most stable conformation of cis-1-4-diethylcyclohexane has 1 both substituents equitorial 2 both substituents axial 3 one substituent axial one equitorial

Answer 50

3 one substituent axial one equitorial

Question 51

infrared spectroscapy probes molecular vibrations rotations translations

Answer 51

vibrations due to existence of dipole moment

Question 52

acid catalyzed dehydrations of an alcohol is substitution addition elimination

Answer 52

elimination reaction (water eliminated)

Question 53

according to the karplus equation vicinal ¹H-¹H coupling are always large sometimes large never large

Answer 53

sometimes large

Question 54

Tertiary alkyl halides can undergo Sn2 reactions Sn1 reactions both

Answer 54

Sn1 reactions because they for 3\* stable carbo cation

Question 55

which of the following are mirror images of each other pair of enantiomers pair of regioisomers pair of diastereomers

Answer 55

pair of enantiomers

Question 56

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