ORGO Ch. 4 Analyzing Organic Reactions

Question 1

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

Answer 1

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

Question 2

When will an acid-base reaction proceed?

Answer 2

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

Question 3

What is a Lewis Acid?

Answer 3

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

Question 4

What is a Lewis base?

Answer 4

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

Question 5

What is formed when Lewis acid and bases interact?

Answer 5

coordinate covalent bonds

Question 6

What is a bronsted-lowry acid?

Answer 6

a species that can donate a proton (H+)

Question 7

What is a bronsted-lowry base?

Answer 7

a species that can accept a proton (H+)

Question 8

What is amphoteric?

Answer 8

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

Question 9

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

Answer 9

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+

Question 10

What is the acid dissociation constant equation?

Answer 10

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

Question 11

What does a negative and positive pKa mean?

Answer 11

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

Question 12

What are the pKa values of strong acids and bases?

Answer 12

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

Question 13

Which functional groups act as acids?

Answer 13

alcohols, aldehydes and ketones, carboxylic acids and its derivates

Question 14

Which functional groups act as a base?

Answer 14

amides and amines

Question 15

What is the acidic trend in the period table?

Answer 15

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

Question 16

What are the 4 major factors that determine nucleophilicity?

Answer 16

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

Question 17

What happens to the nucleophilic in polar solvent?

Answer 17

it dissolves

Question 18

What is a strong NU?

Answer 18

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

Question 19

What is a weak NU?

Answer 19

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

Question 20

What is an electrophile?

Answer 20

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

Question 21

What is the ranking of electrophilicity of carboxylic acids?

Answer 21

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

Question 22

What is the diff b/w electrophilicity and acidity?

Answer 22

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

Question 23

Why are weak bases good for leaving groups?

Answer 23

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

Question 24

Describe the steps of an SN1 reaction.

Answer 24

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.

Question 25

What is the hallmark of an SN1 vs SN2 reaction?

Answer 25

SN1 - A Racemic mixture SN2 - R/S configuration

Question 26

Describe the steps of an SN2 reaction.

Answer 26

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

Question 27

What is oxidation and reduction?

Answer 27

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

Question 28

What functions group has zero oxidation level?

Answer 28

alkanes

Question 29

What functions group has one oxidation level?

Answer 29

alcohols, alkyl halides, and amines

Question 30

What functions group has two oxidation levels?

Answer 30

aldehydes, ketones, and imines

Question 31

What functions group has three oxidation levels?

Answer 31

carboxylic acids, anhydrides, esters, and amides

Question 32

What functions group has four oxidation levels?

Answer 32

carbon dioxide (CO2)

Question 33

What is an oxidizing agent?

Answer 33

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

Question 34

What are the strong oxidizing agents?

Answer 34

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

Question 35

What can primary alcohols be oxidized to?

Answer 35

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

Question 36

What can secondary alcohols be oxidized to?

Answer 36

ketones using PCC, or CrO3/pyrimidine

Question 37

What are the good reducing agents?

Answer 37

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

Question 38

What makes something a good reducing agent?

Answer 38

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

Question 39

What can aldehydes and ketones be reduced to?

Answer 39

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

Question 40

What can amides be reduced to?

Answer 40

amines using LiAlH4/ether or H+/H2O

Question 41

What can esters and carboxylic acids be reduced to?

Answer 41

primary alcohols and esters using LiAlH4/ether or H2O

Question 42

What is an idol?

Answer 42

2 equivalents of alcohol

Question 43

How are acetals and ketals formed?

Answer 43

acetal = aldehyde + idol ketal = Keton + Idol

Question 44

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

Answer 44

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

Question 45

What is the order of oxidation amongst function groups?

Answer 45

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

Question 46

What can alkanes and aldehydes be oxidized to?

Answer 46

carboxylic acids using H2CrO4, KMnO4, or H2O2

Question 47

What can alkenes and alkynes be oxidized to?

Answer 47

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

Question 48

What can diols be oxidized to?

Answer 48

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

Question 49

What can ketones be oxidized to?

Answer 49

Esters using mCPBA

Question 50

When will a substitution reaction proceed?

Answer 50

when the nucleophile is a stronger base than the leaving group

Question 51

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

Answer 51

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

Question 52

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

Answer 52

I-, Br-, Cl-, F-

Question 53

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

Answer 53

F-, Cl-, Br-, I-

Question 54

What is the most and least stable leaving groups?

Answer 54

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