Organic Chemistry 2

Front 1

What are the general pKa values of the following hydrogens?

Alkyl
Allylic
Benzylic

Back 1

Alkyl ~ 55
Allylic - 43
Benzylic - 41

Front 2

What is the pKa and general structure of:

Amine

Amide

Back 2

Amine - 32-35 (:NH3)

Amide - 15-17 (Like an aldehyde, but the H is replaced with :NR2)

Front 3

Describe the following and how they're made:

Imine (give an example compound with answer)

Enamine

Back 3

Imine is the Nitrogen analog of a carbonyl: the double-bonded Oxygen is replaced with NR3 where R can be alky, hydrogen or a lone pair.
These are also called "Schiff Bases."
Example:
H2N-NH2 (Hydrazine). Used in Wolff-Kishner reaction.

An enamine is the Nitrogen analog of an enol, it generally rearranges to an imine (tautamerization).

Front 4

1) What is the Wolff-Kishner reaction and what does it do?

2) What solvent is used? Why?

3) What is the main favorable characteristic of the Wolff-Kishner reaction?

Back 4

1) It is a reaction with hydrazine (H2N-NH2) in which an aldehyde or ketone is reduced to a methylene group.

2) The solvent used is ethylene glycol because it has a high boiling point and this reaction needs to take place at high temperatures.

3) Instead of using Friedel-Crafts Alkylation (which allows for rearrangements, making the undesired product favorable), you can use Friedel-Crafts Acylation followed by Wolff-Kishner to remove (reduce) the carbonyl oxygen which avoids rearrangements in the net reaction.

Front 5

1) Describe the Wittig reaction.

2) What reagents are used?

3) What product does it prefer?

Back 5

1) The Wittig reaction converts carbonyls into "unambiguous" alkenes that are otherwise hard to produce. It is completely regioselective.

2) Aldehydes or Ketones plus +PPh3CH2- (Phosphorane; a ylid)

3) The (Z) or cis-product

Front 6

What is a ylid?

What is an example?

Back 6

1) A ylid is any compound with opposite charges on adjacent, covalently bound atoms, each of which has an electronic octet.

2) +PPh3C- (Phosphorane)

Front 7

1) What are the compounds LiAlH4 & NaBH4 used for?

2) How do they work?

3) Which is stronger/harsher?

4) Which is more selective?

Back 7

1) Reducing agents.

2) They donate hydride to the compound being reduced. Used for carbonyls: transforms the double-bonded oxygen to a -OH and H group attached to the same carbon. (Remember that a hydride is a hydrogen that carries a lone pair!)

3) LiAlH4 is stronger, it will reduce everything possible. (Not sure if it reduces aromatics).

4) NaBH4 is more selective, it will only reduce the most acidic group.

Front 8

1) What is Phosphorane?

2) How is it made?

3) Can it be made from tertiary halides? Why or why not? (Think about the structure of PPh3)

Back 8

1) A ylid (+PPh3CH2-)

2) It is made by first reacting PPh3 (triphenyl phosphine) with the desired alkyl halide (can't use tertiary, only secondary and primary) to create a phosphonim salt. Then react the phosphonium salt with butyllithium to create Phosphorane.

3) It cannot be made from tertiary halides due to steric reasons.

Front 9

1) Name some reducing agents.

2) What is each one used for?

Back 9

1) a)LiAlH4 (LAH); NaBH4: Used to reduce carbonyls to alcohols. LAH is harsh and completely reduces all available groups. NaBH4 is gentler and more selective.

b)LiNH3: LiNH3 selectively reduces alkynes to trans-alkynes

c) Lindlar's catalyst + H2: selectively reduces alkynes to cis-alkynes

d) H2 + Pd/C: completely reduces double-bonds

Front 10

What is the difference between NaNH2 and NaNH3(liquid) or LiNH3(liquid)?

Back 10

NaNH2 is used to deprotonate a terminal alkyne via a free radical-like reaction. BuLi can be used, as well, but this mechanism is via the organometallic pathway.

LiNH3(liquid) and NaNH3(liquid) cause reduction of internal alkynes to trans-alkenes. Lindlar's catalyst is used to reduce internal alkynes to cis-alkenes.

Front 11

a) What is this?

b) What is it used for?

Back 11

a) A phosphorane ylid.

b) It is used in the Wittig reaction

Front 12

What is a hydrate?

Back 12

A hydrate is an identical molecule with a molecule of water added. Not like a protonated alcohol, from my understanding.

Example:

Ethanol (CH3–CH2–OH) can be considered as a hydrate of ethene (CH2=CH2).

Front 13

What is the order of precedence for naming?

REMEMBER: this is NOT necessarily the order of reactivity (need to research this, I think acid chlorides are more reactive than anhydrides and stuff)

Back 13

1) Carboxylic acid
2) Anhydride
3) Ester
4) Acid Halide
5) Amide
6) Nitrile
7) Aldehyde
8) Ketone
9) Alcohol/Phenol
10) Thiol
11) Amine
12) Large Alkyl
13) Small Alkyl

Front 14

Name some ortho/para directing groups.

Back 14

1) Alkyls
2) Hydroxyl
3) Amino
4) Acylamino
5) Alkoxy
6) Phenyl
7) Halogens (special case)

Front 15

Name some meta directing groups.

Back 15

1) Carboxy
2) Carboxamido
3) Carboalkoxy
4) Acyl
5) Sulfonic acid
6) Cyano
7) Nitro

Front 16

Halogens are what kind of directing group? Why?

Back 16

Ortho/para, because their electron withdrawing effects are most prominent on π-bonds; they can be electron donators for π-bonds. Because they're good leaving groups, the positive charge can fall onto the carbon they're attached to, allowing them to leave the molecule.

Front 17

Name some Electron Withdrawing Groups (EWGs).

Back 17

1) Aldehyde
2) Ketone
3) Ester
4) Cyano
5) Nitro
6) Halides (special case, they're EWG to σ-bonds, but EDG to π-bonds)

Front 18

In reference to substituents on aromatic rings, name some Electron Donating Groups (EDGs).

Back 18

1) Alkyl
2) Hydroxyl (OH)
3) Alkoxy (OR)
4) Amine (:NH2, :NR2, :NHR)

Front 19

What is the criteria for aromaticity?

Back 19

1) 4n+2π-electrons
2) Cyclic structure
3) Overlapping p-orbitals (this usually means sp2 hybridized)
4) Conjugated π-electron system

Front 20

What is the criteria for anti-aromaticity?

Back 20

1) 4n π-electrons
(there's more that I don't remember)

Front 21

What are two specific traits that cause a substituent to be an ortho/para director? Why?

Back 21

1) An unshared electron lone pair on an atom directly connected to the benzene ring because the lone pair can be involved in the resonance stabilization of the carbocation intermediates.

2) An alkyl group directly attached to the benzene ring because one resonance structure will be a tertiary carbocation which stabilizes the intermediate.

Front 22

What are the three criteria for activating/deactivating groups?

Back 22

1) All meta-directing groups are deactivating groups.

2) All ortho/para-directing groups (except for the Halogens) are activating groups.

3) The halogens are deactivating groups.

Front 23

If a benzene contains an EWG and an EDG in positions that oppose where they direct a new substituent, which group wins and why?

Back 23

EDG because the resonance effect is stronger than the polar effect.

Front 24

What governs the nucleophilicity of halide ions in polar, aprotic solvents? Why?

Back 24

Basicity. The most basic ion is the most nucleophilic. I think this has to do with the fact that there are no hydrogens to hydrogen bond with in aprotic solvent, so the halide is free to use it's electrons as a nucleophile.

Front 25

What is NaH used for?

Back 25

It is very basic, it is a source of hydride ion. Turns alcohols into alkoxide and allows H2 gas to bubble out of the reaction mixture.

Front 26

What is the difference between nucleophilicity and basicity?

Back 26

Nucleophilicity is based on kinetics. It deals with how fast something will react. It depends on the solvent the nucleophile is in (protic solvents can decrease nucleophilicity by engaging lone pairs in h-bonding). (NEXT SIDE)

Hint 26

Basicity is thermodynamic which means it deals with the stability of the reactants vs. the products. Basicity is not dependent on the solvent it's in.

Front 27

What is the purpose of a 3Å Molecular Sieve?

Back 27

To absorb water from the reaction to allow it to go to completion and prevent the reaction from reversing due to hydrolysis.

Front 28

What is saponification?

Back 28

Hydrolysis of esters under basic conditions. It turns esters into carboxylic acids.

Front 29

What is a desiccant?
Give an example of one.

Back 29

A desiccant is used for dehydration. P2O5 (which comes from P4O10) is a desiccant used to convert carboxylic acids into anhydrides.

Front 30

1) What is PCC?

2) What is it used for?

3) What is it made of?

Back 30

1) Pyridinium chlorochromate. It is an oxidizing agent.

2) It converts primary alcohols into aldehydes and secondary alcohols into ketones.

3) Mix pyridine with HCl (hydrochloric acid) and CrO3 (chromate).

Front 31

What is the reactive intermediate in most addition to carboxylic acid reactions?

Back 31

A tetrahedral addition intermediate.

Front 32

Rank these seven functional groups in order of decreasing reactivity:

Acids,esters
Amides
Acid chlorides
Nitriles
Ketones
Anhydrides
Aldehydes

Back 32

Most

1) Acid chlorides
2) Anhydrides
3) Aldehyde ~ Ketone
4) Acids & Esters (carboxy groups)
5) Amides
6) Nitriles

Least

Front 33

What happens when you mix an aldehyde or a ketone with a tertiary amine?

Back 33

Nothing. Only primary and secondary amines react with aldehydes and ketones because the amine must have an alpha-hydrogen to lose to allow stabilization.

Front 34

What are the important things to remember about the Wolff-Kishner reaction?

Back 34

1) It is a condensation (loses water) followed by an elimination under basic conditions.

2) Hydrazine is used on an aldehyde or ketone (H2N-NH2)

3) BEFORE the base reacts, the Nitrogen closest to the carbonyl group loses all it's hydrogens to form an imine.