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Ochem 333 Charonnat > ochem final > Flashcards

ochem final Flashcards

1
Q

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
A
  1. the leaving group departs from the alpha carbon in the first step
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2
Q

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

1 r

2 s

3 neither

A

R

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3
Q

which of the following reactions exhibits primary kinetic isotope effect>

  1. Sn2
  2. E1
  3. E2
A

3 E2

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4
Q

which reactions are entropically favored

  1. eliminations
  2. substitutions
  3. additions
A

1 Eliminations

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5
Q

(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
A

1 -41*

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6
Q

which compound is the most reactive toward nuclephilic substitution

1 1,2- epoxypropane

  1. 1-methoxypropane
  2. propan-1-ol
A

3 propanol

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7
Q

alchohols can act as

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

3 either acid or bases

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8
Q

Sn1 reactions afford

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

2 racemization or partial inversion of configuration

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9
Q

phenols are more acidic than alchohols due to

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

2 resonance stabilization of the corresponding conjugate base

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10
Q

which carbo cation is the least stable?

A

1

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11
Q

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

A

hex-1-ene

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12
Q

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

A

1

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13
Q

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
A

2 acyclic alkyne

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14
Q

Simmons Smith cyclopropanation of 1,2disubstituted alkenes is

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

2 completely diastereoselective

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15
Q

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

1 1H

  1. 13C
  2. both have the same population excess
A

13C

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16
Q

Sn2 reactions occur with

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

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.

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17
Q

PCC oxidation of a primary alchohol affords the corresponding

  1. carbocylic acid
  2. aldehyde
  3. ester
A
  1. 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.
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18
Q

Oxidation of 1-butanethiol with dilute hydrogen peroxide yields

  1. 1 an alcohol
  2. sulfide
  3. disulfide
A

. You will get from here an alcohol.

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19
Q

epoxides are reactive compounds due to

angel strain

torsional strain

steric strain

A

Angel strain

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20
Q

which of the following compounds is an aromatic

A

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

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21
Q

which reaction often yields product mixtures due to rearrangements

Sn1

Sn2

E2

A

Sn1

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22
Q

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

slower ‘

faster’

same rate

A

Slower

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23
Q

the stereochemical configuration ofthe following diol is

A

S

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24
Q

the following reaction is

A

partially enantioselective and completely diastereoselective

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25
Q

which of the following reagents is the most nucleophilic

A

EtO-Na +

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26
Q
A

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

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27
Q

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

  1. reaction of hydrogen gas and catalitic palladium on charcoal with E)-hept-2-ene
A

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

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28
Q

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

A
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29
Q

if a compounds molecular formula is C9 H14O2 it posesses

3, 4, or 5 degrees of unsaturation

A

3

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30
Q

which bond vibration is expected to have the most intense infrared absorption

C-D

C-Cl

C-N

A

C-D

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31
Q

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

  1. nitrogen
A

2 chlorine

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

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32
Q

A CARBONYL functional group stretching absorbtion is

1 weak

2 moderate

3 strong

A

3 Strong

33
Q

the harmonic oscillator model contains a potentional energy that is

1 completely symmetrical

  1. primarily symetrical but with an unsymmetrical component
  2. completely unsymmetrical
A
  1. primarily symetrical but with an unsymmetrical component
34
Q

which of the following species cannot be observed by mass spectrometer

1 a cation

2 radical cation

3 radical

A
  1. cation
35
Q

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

  1. smaller T1 and smaller Y values

4 Smaller T1 and larger Y values

A

2 larger T1 and smaller Y values

36
Q

Staggered and eclipsed ethane differ in

configuration

consitution

conformation

A

conformation ‘

37
Q

the most stable radical is

A
38
Q
A

2 . Sp3, Sp2 Sp

39
Q

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

A

6X faster

the reaction is second order

40
Q

(S)-1-chlorobutan-2-ol posseses

1 four sets of chemically equivalent protons

five sets

seven sets

A

2 five sets of chemically equivalent protons

41
Q

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

A

1 much more than the energy of a typical covalent bond

42
Q

organic compounds containing nitrogen

1 always have an even molecular weight

always have an odd MW

can either have even or odd MW

A

can either have even or odd MW

43
Q

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
A
  1. a smaller m/z value than the molecular Ion
44
Q

which spectrometric technique can be used to determine molecular connectivity

1 IR

  1. NMR
  2. UV-VIS
A

NMR

45
Q

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

increases

decreases

remains constant

A

Increases

µ=m1m2/m1+m2

46
Q

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

A

always the molecular ion

47
Q

(2R, 5S) -5-bromohexan2-ol and (2R, 5r) -5-bromohexan2- ol are

1 diastereomers

2 enantiomers

  1. refioisomers
A
  1. diastereomers
48
Q

Sn2 reactions proceed with

  1. racemization
  2. rentention of configuration
  3. inversion of configuration
A

3 inversion of configuration

49
Q

protons have different chemical shifts due to

  1. spin-spin coupling
  2. different local induced magnetic fields
  3. different external magnetic fields
A
  1. different local induced magnetic fields
50
Q

the most stable conformation of cis-1-4-diethylcyclohexane has

1 both substituents equitorial

2 both substituents axial

3 one substituent axial one equitorial

A

3 one substituent axial one equitorial

51
Q

infrared spectroscapy probes molecular

vibrations

rotations

translations

A

vibrations

due to existence of dipole moment

52
Q

acid catalyzed dehydrations of an alcohol is

substitution

addition

elimination

A

elimination reaction (water eliminated)

53
Q

according to the karplus equation vicinal 1H-1H coupling are

always large

sometimes large

never large

A

sometimes large

54
Q

Tertiary alkyl halides can undergo

Sn2 reactions

Sn1 reactions

both

A

Sn1 reactions

because they for 3* stable carbo cation

55
Q

which of the following are mirror images of each other

pair of enantiomers

pair of regioisomers

pair of diastereomers

A

pair of enantiomers

56
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Ochem 333 Charonnat (1 decks)

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