Organic Chem Reactions to Know

Homolytic vs heterolytic cleavage of bonds

• Homolytic: produces two radical species

• Heterolytic: Both electrons go to one species → can produce carbanions, carbocations, hydrides and protons

What are the 7 types of reactions we need to know?

1. Nucleophilic substitution

2. Aldol condensation

3. Claisen condensation

4. Decarboxylation of B-Keto Acids

5. Rearrangements or Isomerization

6. Eliminations

7. Free Radical Reactions

In a nucleophilic sub, what is involved?

• Good LG

• Good nuc

• Electrophile

• Usually S_N2

S_N2 is called an __ mechanism, while S_N1 is a __ mechanism

Associative, dissociative

Common nucleophiles have…

High e- density and are sometimes negatively charged

Give an example of some biological nucleophiles

• Negatively charged oxygen

• Negatively charged sulfhudryl (a deprotonated -SH group)

• Carbanion

• Amine

• Hydroxide

• Imidazole

Give some examples of biological electrophiles

• Carbonyl C

• Phosphorus of phosphate group

• Proton

• Protonated imine group

Enzymes often create __ leaving groups on substrates

Better

What are two examples of good leaving groups?

Pyrophosphate or phosphate, H₂O

How does hexokinase phosphorylate glucose?

There’s a general base as a side chain in the active site that deprotonates the -OH on C6, whose e- then attack the gamma P in ATP.

In glycolysis, we do __ aldol, in gluconeogenesis, we do __ aldol.

Reverse, forward

An aldol condensation turns a __ into a __

Ketone into an alcohol

A claisen ester condensation turns an __ into a __

ester into a ketone

Name two significant properties of carbonyls. Similar to carbonyls in this regard are…

• The O is very e- withdrawing

• They can stabilize adjacent carbanions via resonance

• Imines!

List the steps of an aldol condensation reaction

1. Carbanion formation

2. Nucleophilic attack

3. Protonation

What is a biological example of an enzyme that utilizes aldol condensation. What about claisen condensation?

• Aldol: Aldolase

• Claisen: Thiolase

Are thioesters more or less stable than esters?

Less! Bad 3p and 2p S/C overlap

__ is an __ inhibitor of Thiolase, because you can’t hydrolyze off the covalent attachment between the cysteine in thiolase and the C in __.

Iodoacetate is an irreversible inhibitor of thiolase, because it irreversibly covalently attaches to a cysteine residue in the active site

Decarboxylation reactions yield…

Carbon dioxide

What’s an example of an enzyme that catalyzes an isomerization?

• Phosphohexose isomerase

• Triose phosphate isomerase (enediol intermediate)

What’s an example of an enzyme that catalyzes an elimination?

Enolase (involves metal ion catalysis)

Free radical reactions are often used to…

Break C-C bonds