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MCAT Chemistry by me > Organic Chemistry > Flashcards

Organic Chemistry Flashcards

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1
Q

Characteristics of a good nucleophile

- basicity and electronegativity

A

strong base
weak electronegativity (opposite of EN)
increase left in the periodic table
so C- > N- > O-

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2
Q

Characteristics of a good leaving group

  • in terms of basicity
  • how it relates to nucleophilicity
A

Lots of shells - down the periods
weak base - conjugate of a strong acid
opposite of nucleophilicity

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3
Q

In nucleophilic substitution, given that there are two nucleophiles, which one will leave and which one will remain?

A

the stronger nucleophile will remain and the weaker one will leave

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4
Q

When would alcohol act as a nucleophile versus an acid?

A

has EWG or EDG

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5
Q

Ways to make alcohol into good leaving groups

A

Protonation or sulfonation

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6
Q

How to protect the alcohol and prevent it from acting as an acid

A

sulfonation - make into a methylate or tosylate

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7
Q

How to determine the reactivity of carbonyls

A

more positive the carbonyl, more reactive it is

more positive it is, more likely it will get attacked

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8
Q

Sigma bonds

  • where the electrons are localized
  • strength of the bond, stability, and energy released
A

electrons are localized directly between the nuclei

very stable, lots of energy released, low energy level

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9
Q

pi bonds

  • where the electrons are localized
  • strength of the bond, stability, energy released
  • atoms that form pi bonds
A

not close to the nucleus, top and bottom

reactive, weaker bond, reactive
- O, S, P tend to form pi bonds

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10
Q

If a bond has more “s” character, what does it say about the length, strength, and stability?

A

shorter, stronger, and more stable

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11
Q

According to the VSPER theory, how are the angles determined?

A

angles that minimize the repulsive forces between the atoms

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12
Q

How to lone pairs and pi electrons distort the predicted bond angles?

A

lone pairs and pi electrons require more room than bonding pairs, so they distort the predicted bond angles

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13
Q

How many atoms are the delocalized electrons shared by?

A

shared by 3 or more atoms

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14
Q

T/F: resonance only results from pi bonds and lone pairs

A

T

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15
Q

What is resonance energy?

A

the difference between the energy of the real molecule and the energy of the most stable Lewis structure

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16
Q

What are the rules about the number of atoms, unpaired electrons, and resonance atoms in the rules of drawing resonance structures?

A

atoms are where they were

the number of unpaired electrons must remain the same

the resonance atoms must lie in the same plane

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17
Q

What is the stability of the resonance structure determined by?

A

Determined by a resonance structure that contributes the most - the most stable resonance form with the lowest formal charge with less charge separation in the molecule

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18
Q

How does the stability of the conjugate base relate to the acidity of the acid?

A

More stable the conjugate base, more stronger the acid

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19
Q

Requirements to be “aromatic”

A

cyclic

planar

4n+2 number of pi electrons

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20
Q

What does it mean when a molecule is aromatic?

A

increased stability of a cyclic molecule due to the electron delocalization

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21
Q

Structural isomer

A

bond to bond connectivity

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22
Q

Eclipsed vs. fully eclipsed conformer

A

fully eclipsed - steric functional groups are eclipsing one another

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23
Q

gauche conformer

A

steric functional groups are right next to each other front and back

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24
Q

anti-staggered conformer

A

steric functional groups are anti to one another front and back

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25
Q

what is a relative configuration?

A

two molecules are said to have the same relative configuration if the orientation of all the substituents are the same except for one substituent.

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26
Q

How do R and S enantiomers differ?

A

they differ on how they rotate the plane polarized light

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27
Q

what is a plane polarized light

A

light with electric fields oriented in the same direction

28
Q

what does it mean when a compound is optically active?

A

the compound rotates the plane polarized light to a certain degree. in other words, light with electric fields oriented in the same direction is rotated to a certain degree and direction.

29
Q

what is compound’s observed rotation?

A

Observed rotation includes the degree and direction of rotation of the electromagnetic field

30
Q

what is a specific rotation?

A

a standardized form of observed rotation that is calculated from the observed rotation and experimental parameters.

31
Q

what is an optical purity?

A

the ratio of actual rotation to the rotation of pure sample

32
Q

what are diastereomers?

connectivity? formula? mirror images? same compounds?

A

same connectivity, same formula but not mirror images; NOT the same compounds

33
Q

Do diastereomers differ in physical and chemical properties?

A

different compounds - have different physical and chemical properties

34
Q

what is the maximum number of optically active isomers that a single compound can have given an “n” number of chiral centers

A

the maximum number of optically active isomers a compound can have given “n” chiral centers is 2^n

35
Q

What are meso compounds?

are they chiral? do they rotate plane-polarized light?

A

internal mirror images

achiral, do not rotate plane-polarized light

36
Q

What are epimers?

A

epimers are diastereomers that differ in configuration at only one chiral center

37
Q

what are anomers?

A

anomers are cyclic diastereomers - when a ring closure occurs at an epimeric carbon

38
Q

What are cis/trans isomers?

A

special diastereomers that exist due to multiple bonds or a ring structure

39
Q

do cis and trans isomers have different physical properties?

A

cis and trans isomers have different physical properties because cis has a dipole moment whereas trans does not

trans isomers stick more easily; thus, have higher mp and bp than cis isomers

40
Q

how to determine cis or trans isomers (E or Z)

A

determine high or low priority groups on each carbon, then identity how the high and low priority groups are distributed among the different carbons

same side: Z
opposite sides: E

41
Q

what are the different kinds of diastereomers?

A

configurational diastereomers - epimers

cis/trans diastereomers - cyclic or multiple bonds

42
Q

in order of reactivity:

amides, aldehydes, ketones, anhydrides, esters, carboxylic acids, acyl halides

how to determine this reactivity

A

acyl halides > aldehdes ketones > anhydrides > esters > carboxylic acids > amides

by examining the reactivity of the leaving groups; more stable the leaving group is in solution, more likely the nucleophilic substitution will take place

43
Q

what condition is needed for hydrolysis of amides to make carboxylic acids?

A

extreme condition is needed

high temperature, strong acid

this is unlikely to occur in biological systems

44
Q

what is important in achieving transesterification?

A

it is important to add excess alcohol you want to substitute in

45
Q

in aldehyde and ketone tautomerization, which tautomer form is more stable?

A

keto (aldehyde/ketone) is more stable form because the enol is weakened by the electronegativity of the oxygen

46
Q

what can tautomers catalyzed by?

what happens during tautomerization?

A

acid or base

deprotonation of the alpha carbon and protation of the carbonyl carbon

47
Q

Describe the strength difference between NaBH4 and LiAlH4

A

Only LiAlH4 is strong enough to fully reduce carboxylic acids,esters, and acetates to alcohols

But both can reduce aldehydes and ketones, and acyl halides to alcohols

48
Q

how to form carboxylic acid from acyl chloride

A

acyl chloride + nitriles (CN-), becomes, cyanohydrin

cyanohydrin is converted to carboxylic acid when exposed to water and acid

49
Q

what’s more stable enamine or enols?

A

enamines are more stable than enols as nitrogen is less electronegative and less electron withdrawing than oxygen

50
Q

How are enamines and imines formed?

A

acid catalyzed addition of amines

depending on if there is hydrogen available on the amine, it will be imine or enamine. Imine if there is hydrogen available on the amine

51
Q

can there be a tautomerization between imine and enamine

A

only when the original amine is primary. this happens on the nitrogenous bases of nucleotides

52
Q

when carboxlic acid gets reduced to alcohol, what does it become first?

A

gets reduced to aldehyde, then alcohol, then to alkene, to lakane

53
Q

when alcohols get oxidized, what do they become first?

A

alcohols become oxidized to aldehydes then to carboxylic acids

54
Q

Reduction of carboxlic acids and esters by NaBH4

A

No reaction

55
Q

reduction carboxylic acids by two equivalents of LiAlH4

A

alcohol

56
Q

how many LiAlH4 equivalents are needed to reduce carboxlic acids to alcohol?

A

2

57
Q

how many LiAlH4 equivalents are needed to reduce aldehyde and ketone to alcohol?

A

1

58
Q

how many NaBH4 equivalents are needed to reduce aldehde and ketone to alcohol?

A

1

59
Q

when is hydrogen electronegative versus electropositive in a molecule?

A

electronegative when bonded to anything left of boron on the periodic table

electropositive when bonded to anything right of the carbon on the periodic table

60
Q

MnO4 2-, CrO4 2-, Cr2O7 2-

vs.

PCC

A

PCC is a gentler oxidizing agent so it’ll only oxidize primary alcohol to aldehde and secondary alcohol to ketone

permanganate, chromate, and dichromate are strong oxidizing agents so they will oxidize primary alcohol all the way to carboxylic acids

61
Q

what happens when phosphoric acid is heated?

A

forms phosphoric anhydrides

62
Q

phosphoric acids reaction with alcohol

A

phosphoric acids react with alcohol to form esters

63
Q

oxidation

A

increasing bonds to oxygen, halogens, loss of C-H bonds

losing electron density

64
Q

reduction

A

increase in bonds with hydrogen or carbons. Loss of bonds to oxygen or halogen

65
Q

can tertiary alcohol be oxidized?

A

no

66
Q

why is it easier to decarboxylate when the beta-carbon is a carbonyl?

A

because the anion intermediate is resonance stabilized or the acid forms a more stable cyclic intermediate

MCAT Chemistry by me (8 decks)

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