Synthesis Reactions

Bronsted-Lowry Acid-base reactions

Bronsted Acid: Proton donor (H+ donor)

Bronsted Base: Proton acceptor (H+ acceptor)

Conjugate Acid- formed from base

Conjugate Base- formed from acid

Weak, Stable base = Strong, Unstable conjugate acid

Weak, Stable Acid = Strong, Unstable conjugate base

Equilibrium favors weak, stable acids AND/OR equilibrium favors most stable conjugate base

Hydration

Alkene Addition Reaction

1. Nucleophilic pi bond attacks an electrophilic atom.

2. Nucleophile attacks electrophilic carbon.

3. Deprotonation

H2SO4, H2O

Follows Markovnikov's Rule

Final Product: C-OH on the MORE substituted carbon. This is a racemic mixture because the OH group can attack from the top or the bottom.

Halogenation

Alkene Addition Reaction

1. Nucleophilic pi bond attacks an electrophilic atom.

2. Halogen donates electron density back

3. Nucleophile attacks electrophilic carbon.

Br2

Creates a halonium ion intermediate

Final Product: A halogen is attached to both carbons.

Halohydrin Formation

Alkene Addition Reaction

1. Nucleophilic pi bond attacks an electrophilic atom.

2. Halogen donates electron density back

3. Nucleophile attacks electrophilic carbon.

4. Deprotonation

Br2, H2O

Creates a halonium ion intermediate and the OH group follows Markovnikov's Rule and attached to the more substituted carbon.

Final Product: OH on the MORE substituted carbon. A halogen is attached to the LEAST substituted carbon.

Hydroboration-Oxidation (first step mechanism)

Alkene Addition Reaction

1. BH3 2. NaOH, H2O2

Follows Anti-Markovnikov's Rule. Boron and Hydrogen both form bonds across the alkene at the same time therefore it is a SYN addition

Final Product: BH2 on the LEAST substituted carbon. OH replaces BH2. A halogen is attached to the MORE substituted carbon.

Syn Dihydroxylation (OsO4)

Alkene Addition Reaction

Oxidation Reaction

1. OsO4 2. NaHSO3, H2O

Syn- Same side Diol- 2 alcohol

Addition of two alcohol groups SYN across the double bond

Final Product: 2 OH groups on the same side (either 2 wedges or 2 dashes) of the carbons.

Ozonolysis

Alkene Addition Reaction

Oxidation Reaction

1. O3 2. CH3SCH3 (or Zn, H2O)

Cleavage of an alkene, forming a carbonyl on both sides. Split the double bond down the middle and attach an Oxygen to each end of the double bond.

Final Product: 2 carbonyls

(C=O is a carbonyl)

Epoxidation (mCPBA and from the halohydrin)

Alkene Addition Reaction

Oxidation Reaction

mCPBA

Formation of a strained ether called an 'epoxide' from an alkene

Final Product: Has ring strain. Adds 1 oxygen on the same side of the molecule bonded to both carbons.

Hydrogenation Reduction (H2, Pd/C)

Alkene Addition Reaction

Reduction Reaction

H2, Pd/C

SYN addition of Hydrogens across a double bond

Adds 2 Hydrogens on the same side of the molecule bonded to each carbon.

Deprotonation of Alkynes

Alkyne Chemistry

NaNH2

Deprotonates the alkyne

Nucleophile: deprotonated alkyne

Electrophile: alkyl halide

Final Product: A deprotonated alkyne

Note: Equilibrium favors weaker acids with higher pKa values.

Carbon-Carbon bond formation from acetylide anions

Alkyne Chemistry

BrCH2CH3, halogen-carbon chain

Attacks the electrophile

Nucleophile: deprotonated alkyne

Electrophile: alkyl halide

Final Product: An Alkyne with more newly added carbons

Hydration (tautomerization mechanism)

Alkyne Chemistry

HgSO4, H2SO4, H2O

Creates a Markovnikov enol that tautomerizes

Final Product: ketone

(C=O on the MORE substituted carbon)

know the tautomerization mechanism

Hydroboration, Oxidation (tautomerization mechanism)

Alkyne Chemistry

1. BH3 or R2BH (R is sterically bulky) 2. NaOH, H2O2

Creates an Anti-Markovnikov enolate that tautomerizes

Final Product: aldehyde

(C=O on the LESS substituted carbon)

know the tautomerization mechanism

Hydrohalogenation

Alkyne Chemistry

HBr or 2 mol HBr

Creates a Markovnikov product OR a double Markovnikov product

Final Product: reduces an Alkyne to an Alkene with HBr and reduces an Alkene to an Alkane with 2 mol HBr PLUS it adds a halogen

(C-Br on the MORE substituted carbon)

Halogenation

Alkyne Chemistry

Br2 or 2 eq Br2

Creates a TRANS product OR a double TRANS product

Final Product: reduces an Alkyne to an Alkene with 2 halogens added trans of the molecule and reduces an Alkene to an Alkane with 2 mol halogen with 4 halogens added trans of the molecule

(Br attack on opposite sides of the molecule)

Complete Reduction (H2, Pd/C)

Alkyne Chemistry

H2, Pd/C

Completely Reduces to only sigma bonding

Final Product: Reduces an Alkyne to an Alkane with 2 added hydrogens across the double pi bond twice (both carbons on both sides of the triple bond get an added H2)

NOTE: under these conditions, you cannot stop after the first reduction.

Cis- Reduction (H2, Lindlar)

Alkyne Chemistry

H2, Lindlar's Catalyst

SYN addition of H2 across a double pi bond

Final Product: Reduces an Alkyne to an Alkene with 1 added hydrogen across the double pi bond on the same side

(both carbons on both sides of the triple bond get one added H)

NOTE: poisons the catalyst

Trans- Reduction (Na, NH3)

Alkyne Chemistry

Na, NH3 (This is sodium metal, ammonia)

ANTI addition of H2 across a double pi bond

Final Product: Reduces an Alkyne to an Alkene with 1 added hydrogen across the double pi bond on the opposite side (both carbons on both sides of the triple bond get one added H).

Radical Halogenation of alkanes

Radical Chemistry

1. Br2 2. light (hv), or heat (Δ), or ROOR

HIGHLY selective radical reagent

1.) A hydrogen atom is pulled off, leaving a radical in its place

2.) A halogen then adds at the radical position

Final Product: One halogen is added at the radical position

Radical Anti-markovnikov addition of HX

Radical Chemistry

1. HBr 2. light (hv), or heat (Δ), or ROOR

Creates an Anti-Markovnikov product

Final Product: Puts the halogen on the LEAST substituted carbon and puts a radical on the MORE substituted carbon.

SN1

Alkyl Halides

Step by step reaction

Rate = k [RX]

Alkyl Halides: Prefers the more substituted carbon because there is more carbocation stability. The halides must be either a: 2° or 3°

Nucleophile must be: weak

Stereochemistry: Racemic mixture of enantiomers

Final Product:

SN2

Alkyl Halides

Happens all at once

Rate = k [RX] [Nuc]

Alkyl Halides: Prefers the least substituted carbon because there is the least steric strain. The halides must be either a: Methyl, 1°, or 2°

Nucleophile must be: Strong

Stereochemistry: Inverted

Final Product:

E1

Alkyl Halides

Alkyl Halides: Prefers the more substituted carbon because there is more carbocation stability. The halides must be either a: 2° or 3°

Base must be: Weak, Stable

A weak, stable base means that it is not charged and is stabilized by ARIO

Regiochemistry: Zaitsev's Rule- Most substituted alkene is the major product

E2

Alkyl Halides

Alkyl Halides: Prefers the more substituted carbon because there is more carbocation stability. The halides must be either a: 1°, 2°, or 3°

Base must be: Strong, Unstable

A strong, unstable base means that it is charged and is not stabilized in any way by ARIO

Stereochemistry- Anti-periplanar

Regiochemistry: Zaitsev's Rule- Most substituted alkene is the major product

Formation of Alkynes from dihalides

Alkyl Halides

NaNH2

Alkane to an Alkyne

Final Product: an alkyne is formed by removing the halogen groups and adding bonds in their place

Epoxide Opening: weak nucleophile, acidic conditions

Epoxides

Weak Nucleophile and H+

1.) protonation

2.) nucleophilic attack on less substituted carbon

3. Deprotonate

ANTI- forms a trans-diol

Think SN1: bond lengthens so that the substitution happens at the more substituted carbon

Epoxide Opening: strong nucleophile

Epoxides

Strong nucleophile and H2O

1.) protonation

2.) nucleophilic attack on less substituted carbon

ANTI- forms a trans-diol

Think SN2: reduce sterics and attack the less substituted carbon

Trans diol formation from epoxides

Epoxides

1.) protonation

2.) nucleophilic attack on more/less substituted carbon depending on whether it is a strong (less substituted)or weak (more substitued) nucleophile

3. Deprotonate (if necessary- weak nucleophile and H+)

Final Product: Adds two OH groups trans