Chapter 17: Alcohols & Phenols

Classification of Alcohols

-Primary alcohol: OH on a primary carbon

-Secondary alcohol: OH on a secondary carbon

-Tertiary alcohol: OH on a tertiary carbon

Naming Alcohols

-The longest chain must contain the OH group with the lowest number possible

- For cyclic alcohols, the OH group is always #1, so don't include a number in the name

-Ending of alcohols:- ol

Properties of alcohols & phenols

1. Alcohols and Phenols have high boiling points due to hydrogen bonding

-Boiling point increases as the number of carbons increases

-Branching decreases boiling point

2. Alcohols are weakly acidic

Factors that affect acidity :

-Bulky alkyl groups decrease acidity

- EWGs increase acidity

- The closer the EWG is to the OH = more acidic

Factors that affect the acidity of phenols

-Phenols are more acidic than alcohols

-EDG decrease acidity

- EWG at the O & P positions increase acidity

Preparation of alcohol: Alkyl halide→ Alcohol

• Halogen gets kicked out, OH takes it’s place and the stereochemistry flips.

• Reagent: KOH, Sn2

Preparation of alcohols: From Alkenes : 1.BH3/THF, 2.H2O2/KOH

• OH goes to less substituted

Preparation of alcohols: From Alkenes : 1.OSO4/ pryidine , 2. NaHSO3/H2O

or

1. OSO4/THF, 2. Nmo or kmno4/koh

• CIS OH/OH

Preparation of alcohols: From Alkenes : 1. Hg(OAc)2/H2O/THF , 2. NaBH4

• OH goes to more substituted carbon

Preparation of alcohols: From Alkenes : 1. mCPBA/ chcl2, 2. H3O+

• Trans OH/OH

Alcohols from reduction of carbonyl compounds

• 1. NaBH4,EtOH, 2. H2O : Only reduces aldehydes & ketones

• 1. LiAlH4/ dry ether, 2. H2O: Only reduces aldehydes, ketones, esters, and carboxylic acids

Mechanism for reduction of carbonyl compounds

• H- attacks the carbonyl carbon, pi bond breaks, negative charge from O goes to H ( protonation)→ product is alcohol + h2o

Grignard Addition ( R-MgBr)

• Reagent: 1. R-MgBr, 2. H3O+/ H2O

• Formaldehyde + Grignard gives a primary alcohol

• Aldehyde + Grignard gives a secondary alcohol

• Ketone + Grignard gives a tertiary alcohol

Mechanism for Grignard reaction

• 1. R from R-MgX attacks the carbonyl C

• 2. Pi bonds moves to O-→ O-

• 3. H3O+ protonates O—→ OH

Halogenations

• Replaces OH with the halogen ( Cl, Br, I, etc

• H-Cl—→ Cl on the product

• H-Br—→ Br on the product

• H2SO4/NAI—→ I on the product

• SoCl2/ prydine—→ Cl on the product

• PBr3——→ Br on the end product

Halogenation mechanism

PBr3 mechanism

• O attacks P—→ Br- bond breaks (leaves)—→ Br- attacks carbon on the O by SN2—→ OH group is replaced by Br

Tosylation

• Reagent: 1. TsCl, 2. pyridine

• convert OH to OTS

• has no inversion

Mechanism for tosylation

• 1. O from OH attacks S of TsCl

• 2. Cl- leaves

• Pyridine removes H from OH attached to Ts

• 4. Product = R-OTs

Conversion of Alcohols to Alkyl halides

• For Tertiary alcohols use H-Br—→ Product is Br replaces OH

• For primary & secondary alcohols use Pbr3—→ Product is Br replaces Oh

Dehydration of alcohols

• Alcohol—→ alkene by removing H and OH as H2O

• Reagents: H3O+/THF for tertiary alcohols

• Regents: POCl3 for primary & secondary

Dehydration of alcohols mechanism

Oxidation of Alcohols

Partial Oxidation for primary alcohols

Strong Oxidizing agents