Organic Chemistry Ch 4. Analyzing Organic Reactions

Question 1

Lewis acids

Answer 1

Electron acceptors, have vacant orbitals or positively polarized atoms

Question 2

Lewis bases

Answer 2

Electron donors, have a lone pair of electrons and are often anions

Question 3

Bronsted-Lowry acids

Answer 3

Proton donors

Question 4

Bronsted-Lowry abses

Answer 4

Proton acceptors

Question 5

Amphoteric molecules

Answer 5

Can act as either acids or bases depending on reaction conditions, water is a common example

Question 6

Acid dissociation constant

Answer 6

Ka - measure of acidity, it is the equilibrium constant corresponding to the dissociation of an acid, HA, into a proton and its conjugate base (A-)

Question 7

pKa

Answer 7

The negative logarithm of Ka, a lower (or negative) pKa indicates a strong acid, decreases down the periodic table and increases with electronegativity

Question 8

Common acidic functional groups

Answer 8

Alcohols, aldehydes, ketones, carboxylic acids, and carboxylic acid derivatives

Question 9

alpha hydrogens

Answer 9

Hydrogens connected to an alpha carbon, are acidic

Question 10

alpha carbon

Answer 10

Carbon adjacent to a carbonyl carbon

Question 11

Common basic functional groups

Answer 11

Amines and amides

Question 12

Nucleophiles

Answer 12

Nucleus loving and contain lone pairs or pi bonds, they have increased electron density and often carry a negative charge, kinetic property, can be impacted by charge, electronegativity, steric hindrance, and the solvent, common nucleophiles are amino groups

Question 13

Electrophiles

Answer 13

Electron loving and contain a positive charge or are positively polarized, common electrophiles include alcohols, aldehydes, kenos, carboxylic acids, and their derivatives

Question 14

Leaving groups

Answer 14

The molecules fragments that retain the electrons after heterolysis, the best groups can stabilize additional charge through resonance or induction, weak bases (or conjugate bases of strong acids) are also good leaving groups, alkanes or hydrogen ions almost never leaving groups because they form reactive anions

Question 15

Sn1 reaction

Answer 15

Unimolecular nucleophilic substitution, rate depends only on the concentration of substrate, prefer more substituted carbons because the alkyl groups can donate electron density and stabilize the positive charge of the carbocation

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

Question 16

Carbocation

Answer 16

An ion with a positively charged carbon atom

Question 17

Sn2 reaction

Answer 17

Bimolecular nucleophilic substitution, prefer less-substituted carbons because the alkyl groups create steric hinderance and inhibit the nucleophile from accessing the electrophilic substrate carbon, rate dependent on concentrations of both the substrate and the nucleophile

One concerted step where nucleophile attacks at the same time as the leaving group lives, nucleophile must perform a backside attack (leads to inversion of stereochemistry - R to S or vise versa if leaving group and nucleophile have same priority)

Question 18

Oxidation state

Answer 18

The charge an atom would have if all of its bonds were completely ionic, CH4 is the lowest oxidation state of carbon (most reduced) and CO2 is the highest (most oxidized)

Question 19

Oxidation

Answer 19

An increase in the oxidation state and is assisted by oxidizing agents

Question 20

Oxidizing agents

Answer 20

Accept electrons and are reduced in the process, they have a higher affinity for electrons or an unusually high oxidation state, they often contain a metal and a larger number of oxygens

Question 21

Oxidation of primary alcohols

Answer 21

Primary alcohols can be oxidized aldehydes by pyridinium chlorochromate (PCC) or to carboxylic acid by stronger oxidizing agents such as chromium trioxide (CrO3) or sodium or potassium dichromate (Na2Cr2O7 or K2Cr2O7)

Question 22

Oxidation of secondary alcohols

Answer 22

Can be oxidized to ketones by most oxidizing agents

Question 23

Oxidation of aldehydes

Answer 23

Can be oxidized to carboxylic acids by most oxidizing agents

Question 24

Reduction

Answer 24

Decrease in oxidation state and is assisted by reducing agents

Question 25

Reducing agents

Answer 25

Donate electrons and are oxidized in the process, have low electronegativity and ionization energy, often contain a metal and a large number of hydrides

Question 26

Reduction of aldehydes, ketones, and carboxylic acids

Answer 26

Can be reduced to alcohols by lithium aluminum hydride (LiAlH4)

Question 27

Reduction of amides

Answer 27

Can be reduced to amines with LiAlH4

Question 28

Reduction of esters

Answer 28

Can be reduced to a pair of alcohols with LiAlH4

Question 29

Chemoselectivity

Answer 29

Both nucleophile electrophile and oxidation reduction reactions tend to happen at the highest priority or most oxidized functional group, one can make use of steric hindrance properties to selectively target functional groups that might not primarily react or protect functional groups (diols often protecting groups for aldehyde or ketone carbonyls, alcohols can be protected by conversion to tert-butyl ethers)