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MCAT Chemistry > Orgo - General Principles > Flashcards

Orgo - General Principles Flashcards

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1
Q

What condition must be met for an acid-base reaction to take place?

A

It will only proceed if the products formed are weaker than the reactants

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2
Q

What is the definition of a Lewis acid?

A

Electron acceptor in the formation of a covalent bond

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3
Q

What is the definition of a Lewis base?

A

Electron donator in the formation of a covalent bond

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4
Q

What type of covalent bonds do acids and bases form?

A

Coordinate covalent bonds

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5
Q

What is the Bronsted-Lowry definition of an acid?

A

Species that can donate a proton

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6
Q

What is the Bronsted-Lowry definition of a base?

A

Species that can accept a proton

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7
Q

What are amphoteric molecules? Example?

A

Molecules that can either act as Bronsted-Lowry acids or bases
Water

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8
Q

What measures the strength of an acid in solution?

A

The acid dissociation constant

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9
Q

What is the equation of the acid dissociation constant?

A

Ka= [H+].[A-]/[HA]

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10
Q

What is the equation for the pKa?

A

pKa= -log Ka

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11
Q

How does pKa relate to the acidity of an acid? Ranges?

A

The greater the pKa the lower the acidity
pKa < -2 = strong acid
-2 < pKa < 20 = weak acid

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12
Q

What is the acidity trend in the periodic table?

A

Increases down the periodic table because of bond strength
Increases with electronegativity
When these two trends oppose each other, bond strength takes over

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13
Q

What is a special example of protons that are easily lost?

A

alpha Hs on the alpha C of carbonyl

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14
Q

What are 5 functional groups that act as acids?

A
  1. Alcohols
  2. Aldehydes
  3. Ketones
  4. Carboxylic acids
  5. Carboxylic acid derivatives
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15
Q

What are the 2 functional groups that act as bases?

A
  1. Amines

2. Amides

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16
Q

What do nucleophiles have?

A

A lone pair or electrons or pi bonds to form bonds with electrophiles

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17
Q

What is the main distinction between nucleophiles and bases?

A

Nucleophile strength depends on rate of reaction with electrophiles = kinetic property
Base strength depends on equilibrium position of a reaction = thermodynamic property

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18
Q

How do you identify most nuclephiles?

A

CHON with a minus sign or a lone pair

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19
Q

What are the 4 factors that determine nucleophilicity

A
  1. Charge: more negative = better nucleophile
  2. Electronegativity: more electronegative = worse nucleophile
  3. Steric hindrance: larger = worse nucleophile
  4. Solvent: protic solvents can protonate or H bond the nucleophile which decreases its reactivity
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20
Q

What do electrophiles have?

A

Positive charge or positively polarized atom that accepts an electron pair to form bonds with nucleophiles

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21
Q

What is the main distinction between electrophiles and acids?

A

Same as nucleophiles and bases

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22
Q

More positive compounds are more…

A

Electrophilic

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23
Q

What are leaving groups?

A

The molecular fragments that retain the electrons after heterolysis

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24
Q

What can the best leaving groups do?

A

Stabilize additional charge through resonance or induction

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25
Q

What are good leaving groups? Why?

A

Weak bases because they are more stable with an extra pair of electrons

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26
Q

Can alkanes and hydrogen ions be leaving groups? Why?

A

Almost never because they form reactive anions

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27
Q

What are heterolytic reactions?

A

The opposite of coordinate covalent bonding reactions: a bond is broken and both electrons are given to one of the two products

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28
Q

What are the 2 steps of unimolecular nucleophilic substitution reactions (SN1)?

A
  1. The leaving group leaves, forming a carbocation

2. The nucleophile attacks the planar carbocation from either side leading to a racemic mixture of products

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29
Q

What is a carbocation?

A

An ion with C+

30
Q

What does “more substituted C” mean?

A

The carbon with the least amount of hydrogens attached and the most amount of other carbons or other non-hydrogen elements attached

31
Q

What do SN1 reactions prefer? Why?

A

More substituted Cs because the alkyl groups can donate electron density and stabilize the positive charge of the carbocation

32
Q

What is the rate of SN1 reactions only dependent on?

A

The concentration of the substrate

33
Q

In SN1 reactions, which step is the rate limiting one?

A

The first step

34
Q

Why do SN1 reactions form a racemic mixture?

A

Because the incoming nucleophile can attack the carbocation from either side, resulting in varied stereochemistry

35
Q

What is the one concerted step of bimolecular nucleophilic substitution reactions (SN2)?

A

The nucleophile attacks at the same time as the leaving group leaves

36
Q

How is the attack of the nucleophile called in SN2 reactions? Why?

A

Backside attack, because the nucleophile approaches the C at a 180 degree angle to the existing carbon-leaving group bond

37
Q

What happens to the absolute configuration of the molecule when it is attacked by a nucleophile in SN2 reactions?

A

It is changed if the incoming nucleophile and the leaving group have the same priority in the molecule

38
Q

What do SN2 reactions prefer? Why?

A

Less substituted Cs because the alkyl groups create steric hindrance and inhibit the nucleophile from accessing the C

39
Q

What is the rate of SN2 reactions dependent on?

A

The concentrations of both the substrate and the nucleophile

40
Q

How must the nucleophile and leaving group be related in order for a substitution reaction to occur?

A

The reaction will occur when the nucleophile is a stronger base than the leaving group

41
Q

What trends increase electrophilicity?

A

Greater positive charge and better leaving groups

42
Q

What is the oxidation state of an atom?

A

The charge it would have if all its bonds were completely ionic

43
Q

What is the lowest oxidation state of C?

A

CH4

44
Q

What is the highest oxidation state of C?

A

CO2

45
Q

What is the order of functional groups from most oxidized to least oxidized?

A
  1. Carboxylic acids and derivatives
  2. Aldehydes, ketones, and imines
  3. Alcohols, alkyl halides, and amines
46
Q

What happens to the reactants in a redox reaction?

A

Their oxidation states change

47
Q

What is the oxidation state of ions?

A

Their charge

48
Q

What does oxidation mean?

A

Increase in oxidation state = loss of electrons = increase in the number of bonds to O or other heteroatoms

49
Q

What does reduction mean?

A

Decrease in oxidation state = gain of electrons = increase in the number of bonds to H

50
Q

What happens to oxidation agents in redox reactions?

A

They accept electrons and are reduced

51
Q

Are oxidation agents electrophiles or nucleophiles?

A

Electrophiles

52
Q

What do oxidation agents often contain?

A

A metal and a large number of Os

53
Q

What can primary alcohols be oxidized to (2)? By what?

A
  1. Aldehydes by pyrimidinium chlorochromate (PCC)

2. Carboxylic acids by stronger oxidizing agents like chromium trioxide (CrO3) or sodium potassium dichromate (Na2Cr2O7)

54
Q

What are primary, secondary, and tertiary alcohols?

A
  1. Attached to a C with only one alkyl group
  2. Attached to a C with two alkyl groups
  3. Attached to a C with three alkyl groups
55
Q

What can secondary alcohols be oxidized to? By what?

A

To ketones by most oxidizing agents

56
Q

What can aldehydes be oxidized to? By what?

A

To carboxylic acids by most oxidizing agents

57
Q

What happens to reduction agents in redox reactions?

A

They donate electrons and are oxidized

58
Q

Do reduction agents have a low or high electronegativity?

A

Low

59
Q

What do reduction agents often contain?

A

A metal and a large number of hydrides

60
Q

What can aldehydes, ketones, and carboxylic acids be reduced to? By what?

A

To alcohols by lithim alumunium hydride (LiAlH4)

61
Q

What can amides be reduced to? By what?

A

To amines by LiAlH4

62
Q

What can esters be reduced to? By what?

A

To a pair of alcohols by LiAlH4

63
Q

Where do nucleophile-electrophile and oxidation-reduction reactions tend to act?

A

At the highest-priority = most oxidized functional group

64
Q

How can one selectively target functional groups that might not primarily react or protect leaving groups?

A

By making use of steric hindrance properties

65
Q

What groups are often used to protect aldehyde or ketone carbonyls?

A

Diols

66
Q

How can alcohols be protected?

A

By conversion to tert-butyl ethers

67
Q

What are the two reactive centers of a carbonyl containing compound?

A

The carbonyl C and the alpha Hs

68
Q

In which types of compounds are SN1 reactions most likely to occur?

A

Tertiary Cs

69
Q

In which types of compounds are SN2 reactions most likely to occur?

A

Primary Cs

70
Q

What are the 6 steps to problem solving for orgo reactions?

A
  1. Know your nomenclature
  2. Identify the functional groups
  3. Identify the other reagents
  4. Identify the most reactive functional group
  5. Identify the first step of the reaction
  6. Consider stereoselectivity
71
Q

Most anhydrides are… which is caused by…

A

Cyclic because of dehydration of a dicarboxylic acid

72
Q

How are anhydrides formed?

A

One H2O is removed and a bond is formed between 2 carboxylic acid molecules

MCAT Chemistry (17 decks)

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