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kaplan mcat > ORGO Ch. 4 Analyzing Organic Reactions > Flashcards

ORGO Ch. 4 Analyzing Organic Reactions Flashcards

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MCAT flashcards
1
Q

What is the diff b/w Lewis and Bronsted theory?

A

Lewis’s definition is the transfer of electrons, while Bronsted-Lowry’s definition is the transfer of protons

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2
Q

When will an acid-base reaction proceed?

A

only when the conjugate acid and base are weaker than the original reactants

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3
Q

What is a Lewis Acid?

A

An electron acceptor due to vacant p-orbital, and electrophile

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4
Q

What is a Lewis base?

A

An electron donor due to a lone pair that can be donated, and a neutrophile

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5
Q

What is formed when Lewis acid and bases interact?

A

coordinate covalent bonds

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6
Q

What is a bronsted-lowry acid?

A

a species that can donate a proton (H+)

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7
Q

What is a bronsted-lowry base?

A

a species that can accept a proton (H+)

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8
Q

What is amphoteric?

A

species that can act as both a bronsted acid and base such as water, bicarbonate, and dihydrogen phosphate (H2P)

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9
Q

What does water become when it donates and accepts a proton?

A

In an acid solution, water donates a proton, it becomes a conjugated base, OH-
In a basic solution, water accepts a proton, it becomes a conjugated acid H3O+

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10
Q

What is the acid dissociation constant?

A

Ka = [H+] [A]/ [HA]
pKa = - log Ka
where kA is the equilibrium constant for the dissociation of an acid

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11
Q

What does a negative and positive pKa mean?

A

an acidic molecule will have a smaller or negative pKa, and more basic molecules will have a larger pKa

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12
Q

What are the pKa values of strong acids and bases?

A

pKa < -2 are considered strong acids and dissociate completely in aqueous solutions
pKa > -2 are considered strong bases

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13
Q

Which functional groups act as acids?

A

alcohols, aldehydes and ketones, carboxylic acids and its derivates

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14
Q

Which functional groups act as a base?

A

amides and amines

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15
Q

What is the acidic trend in the period table?

A

bond strength decreases down the period table, and acidity (pKa) therefore increases. the more electronegative an atom, the higher the acidity

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16
Q

What are the 4 major factors that determine nucleophilicity?

A

the more negatively charged the molecule is, the better the nucleophile. The more electronegative an atom, the poorer the nucleophile. bulkier molecules and tertiary substrates are less nucleophilic

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17
Q

What happens to the nucleophilic trend in polar solvent?

A

it dissolves

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18
Q

What is a strong NU?

A

HO-, RO-, CN-, N3- > NH3, RCO2-

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19
Q

What is a weak NU?

A

H20, alcohol (ROH), and carboxylic acid (RCOOH)

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20
Q

What is an electrophile?

A

an electron-loving species with a positive charge. acts as a Lewis acid in reactions

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21
Q

What is the ranking of electrophilicity of carboxylic acids?

A

anhydrides are the most reactive, followed by carboxylic acids and esters, and then amides

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22
Q

What is the diff b/w electrophilicity and acidity?

A

electrophilicity and nucleophilicity a kinetic properties, whereas acidity and basicity a thermodynamic property

23
Q

Why are weak bases good for leaving groups?

A

weak bases are most stable with an extra set of electrons that result from heterolysis

24
Q

Describe the steps of an SN1 reaction.

A

the first step (rate-limiting) is when the leaving group leaves, generating a positively charged carbonation, and then the nucleophile attacks that carbonation, resulting in the substitution product in step 2.

25
Q

What is the hallmark of an SN1 vs SN2 reaction?

A

SN1 - A Racemic mixture
SN2 - R/S configuration

26
Q

Describe the steps of an SN2 reaction.

A

in a 1 step reaction, the nucleophile attacks the compound at the same time the leaving group leaves

27
Q

What is oxidation and reduction?

A

oxidation is a loss of electrons (Lewis bases), and reduction is a gain of electrons (Lewis acids)

28
Q

What functions group has zero oxidation level?

A

alkanes

29
Q

What functions group has one oxidation level?

A

alcohols, alkyl halides, and amines

30
Q

What functions group has two oxidation levels?

A

aldehydes, ketones, and imines

31
Q

What functions group has three oxidation levels?

A

carboxylic acids, anhydrides, esters, and amides

32
Q

What functions group has four oxidation levels?

A

carbon dioxide (CO2)

33
Q

What is an oxidizing agent?

A

an element that accepts an electron from another, and becomes reduced.

34
Q

What are the strong oxidizing agents?

A

O2, O3, Cl2, Mn7+, permanganate (MnO4-), chromate (CrO4-), Cr6+, CrO4(2-), Na2Cr2O7, K2Cr2O7, KMnO4, H2CrO4

35
Q

What can primary alcohols be oxidized to?

A

an aldehyde (with a weak oxidizing agent like PCC), or further oxidized to form a carboxylic acid (with a strong oxidizing agent)

36
Q

What can secondary alcohols be oxidized to?

A

ketones using PCC, or CrO3/pyrimidine

37
Q

What are the good reducing agents?

A

H+, H20, Na, Mg, Zn, aluminum (Al), sodium hydride (NaH), calcium dihydride (CaH2), LiAlH4, ether, sodium borohydride (NaBH4)

38
Q

What makes something a good reducing agent?

A

low electronegativity and ionization energy, or contain a hydride (H-) ion

39
Q

What can aldehydes and ketones be reduced to?

A

primary and secondary alcohols using lithium aluminum hydride (LiAlH4)/NaBH4

40
Q

What can amides be reduced to?

A

amines using LiAlH4/ether or H+/H2O

41
Q

What can esters and carboxylic acids be reduced to?

A

primary alcohols and esters using LiAlH4/ether or H2O

42
Q

What is an idol?

A

2 equivalents of alcohol

43
Q

How are acetals and ketals formed?

A

acetal = aldehyde + idol
ketal = Keton + Idol

44
Q

What is the rate-limiting step in an SN1 and SN2 substitution reaction?

A

SN1 - on the concentration of the substrate (1st order)
SN2 - on the concentration of both the substrate and the nucleophile (2nd order)

45
Q

What is the order of oxidation amongst function groups?

A

carboxylic acids and their derivates are the most oxidized, followed by aldehydes, ketones, amines, and lastly alcohols, alkyl halids, and amines

46
Q

What can alkanes and aldehydes be oxidized to?

A

carboxylic acids using H2CrO4, KMnO4, or H2O2

47
Q

What can alkenes and alkynes be oxidized to?

A

carboxylic acids using O3/H202, or KMn04/H30/heat

48
Q

What can diols be oxidized to?

A

aldehydes using NaIO4, Pb(OAc)4, or HIO4

49
Q

What can ketones be oxidized to?

A

Esters using mCPBA

50
Q

When will a substitution reaction proceed?

A

when the nucleophile is a stronger base than the leaving group

51
Q

When is an SN1 vs SN2 reaction most likely to occur?

A

SN1 is most likely to occur o tertiary carbon where the carbonation can be most easily stabilized
SN2 is more likely to occur on methyl or primary carbons because there is less steric hindrance

52
Q

What is the order of the best nucleophiles in a protic solvent?

A

I-, Br-, Cl-, F-

53
Q

What is the order of the best nucleophiles in an aprotic solvent?

A

F-, Cl-, Br-, I-

54
Q

What is the most and least stable leaving groups?

A

the most stable leaving group is H20, and the last is H-

kaplan mcat (28 decks)

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