O Alcohols Are Classified Much Like Alkyl Halides - 1 , 2 , and 3

Chapter 10

 Classification

o Alcohols are classified much like alkyl halides - 1°, 2°, and 3°

 Nomenclature

o Alcohols have precedence over alkenes and alkynes

. Get to the hydroxyl first!

 You do have to say “1” with straight-chain alcohols

H O Br (S,E) 4-bromohex-2-en-1-ol

 When the alcohol is the highest-priority group on a cyclic molecule, then the “1” is implied so you leave it off.

. Don’t worry about the sections naming diols and phenols

 You do need to name diols as “diol,” you just don’t need to call them glycols or anything else weird.

 When you name a cyclic diol, you do need to say the “1”

2-chlorocyclohexan-1,3-diol

 Physical Properties

o Hydrogen bonding causes higher boiling points

o Solubility – small alcohols are miscible with water; larger alcohols are not terribly soluble

 Solubility o Smaller alcohols are miscible with water

o The larger the nonpolar piece, the less soluble the alcohol is in water

o You know this!

 Acidity

o pka – 15-18

o phenol - pka – 10

. Why? The conjugate base, phenoxide, is resonance stabilized

H - - O O O O O + H+ - -

 Formation of Alkoxides

o Acid/base

. Alcohol + very strong base (NaH, NaNH2) → Alkoxide

 If you just use hydroxide or an alkoxide, you will get an equilibrium mixture.

 The hydroxide or alkoxide is not strong enough to quantitatively deprotonate an alcohol (unless it’s a phenol)

o Redox

. Alcohol + alkali metal → Alkoxide

. This is one of the few times when you see Na or K and it’s significant.

 Synthesis Review

. -OH added to primary or methyl alkyl halides

. See Chapter 6 Review

o SN1 . Water added to secondary or tertiary alkyl halides

o Acid-catalyzed hydration of alkenes

. Markovnikov addition of water with rearrangement

o Oxymercuration-demercuration

. Markovnikov addition of water without rearrangement

o Hydroboration-oxidation

. Anti-Markovnikov addition of water

o Addition of OsO4 or KMnO4 to alkenes

. Syn addition of two hydroxyls

o Acid-catalyzed ring-opening of epoxides

. Results in two hydroxyls added anti to one another

o Addition of acetylide ions to carbonyls

 Grignards/Organometallics

o Formation of Grignards and alkyl lithiums

. Magnesium inserts between carbon and halogens

. Lithium replaces the halogen . This is one time where an sp3-hybridized carbon acts the same as an sp2- hybridized carbon.

 This means that this works on any carbon-halogen bond

. Solvent

 There cannot be any acidic protons in the solvent, as the Grignard is such a strong base.

 There cannot be any pi bonds in the solvent as those are sites of reactivity that the Grignard will attack.

. From here on, I will use Grignard to refer to both Grignard reagents and organolithiums, as they do the same things

. The carbon-metal bond is so strongly polar that it’s fine to think of it as ionic.

 Because of this, it’s often easiest to cross out the Li or MgBr and call the R-group an R-

- Ex. CH3CH2MgBr CH3CH2MgBr o Grignards as nucleophiles in SN2 reactions

. Grignards are strong bases/nucleophiles, so they will participate in both

SN2 and E2 reactions

 SN2 with methyl and primary alkyl halides

- CH3MgBr Br CH3

 E2 with secondary and tertiary alkyl halides – no point in using this strong of a base o Grignards attacking carbonyls

. The negatively charged carbon of the Grignard is attracted to the partially positive carbon of the carbonyl . In the following schemes, A and B are just the alkyl pieces attached to the carbonyl-containing molecules and C is the Grignard or other strong nucleophile (such as an acetylide ion)

. Addition of to ketones and aldehydes

O 1) C 2) H+ O H A C A B B

. Addition to esters

O 1) C 2) H+ OH A C A OB C

. Addition to Acid Chlorides

O 1) C 2) H+ O H A C A Cl C o Addition of Grignards to epoxides

. Grignards (and other strong bases) attack the less substituted side of

epoxides in an SN2-like mechanism

O– + O H O H

R- R R