Alcohols Contain a hydroxyl (-OH) group − + Intermolecular forces: dipole-dipole, H-bonding H-bonds between alcohol molecules: high boiling points H-bonds with water: up to 4-carbon alcohols soluble in water -OH group can act as a weak base or a weak acid + Strong base + Strong acid alkoxide alcohol oxonium ion

Alcohol Nomenclature Parent chain = longest chain containing C with -OH Root name: replace –e with –ol ethane  ethanol, butene  butenol, etc. Give –OH the smallest possible number –OH has priority over double bonds, alkyl groups Two –OH groups  -diol; three –OH groups  -triol Add to end of root name (propane  propanediol) 1,2-ethanediol (ethylene glycol) antifreeze 5-methyl-3-hexanol

Alcohol Naming Practice 2-propanol (isopropyl alcohol) 2,4-dimethyl-3-pentanol 3,5-dimethyl-2,4-heptanediol 4-penten-2-ol

Classes of Alcohols Primary (1°) alcohol 1-butanol OH C attached to 1 other C Secondary (2°) alcohol OH C attached to 2 other C’s 4-phenyl-2-hexanol Tertiary (3°) alcohol OH C attached to 3 other C’s 1-methylcyclohexanol

Reactions of Alcohols Reaction with strong bases alcohol as proton donor (weak acid) Reaction with strong acids alcohol as proton acceptor (weak base) Dehydration reverse of hydration of alkenes requires H+ catalyst Oxidation increase # of C-O bonds alkoxide Strong acid oxonium ion H+ - H2O alkene oxidizing agent or aldehyde ketone

Dehydration Mechanism Step 1: electrophilic H+ catalyst attacks nucleophilic O atom Step 2: H2O dissociates, leaving behind a carbocation + H2O Step 3: Electrons from neighboring C-H bond form  bond, regenerating H+ catalyst +

Hydration and Dehydration + H2O Hydration and dehydration are in equilibrium Can change [H2O] to favor one reaction or the other Change Favors Increase [H2O] Formation of Alcohol (hydration) Decrease [H2O] Formation of Alkene (dehydration)

Possible Dehydration Products ? Major product Least H’s on double bond The most-substituted alkene product is favored (most stable)

Oxidation of Alcohols Oxidation: increases oxidation number More C-O bonds (add O) or increases bond order Fewer C-H bonds (remove H) Needs an oxidizing agent CrO3, Cr2O72-, MnO4- ,or PCC (pyridinium chlorochromate) PCC stops at aldehyde 1° alcohol +1 -2 -2 -2 -1 oxidizing agent oxidizing agent +1 +3 +1 -2 +1 +1 +1 aldehyde carboxylic acid CrO3 (Cr6+) Cr3+

Breathalyzer Tests ethanol ethanal ethanoic acid + Cr6+ + Cr3+ oxidized oxidized ethanol ethanal (acetaldehyde) ethanoic acid (acetic acid) + Cr6+ + Cr3+

Breathalyzer Tests ethanol ethanal ethanoic acid + Cr6+ + Cr3+ oxidized oxidized ethanol ethanal (acetaldehyde) ethanoic acid (acetic acid) + Cr6+ + Cr3+ oxidized oxidized methanol methanal (formaldehyde) methanoic acid (formic acid)

Oxidation of Alcohols No reaction 2° alcohol 3° alcohol 2-propanol -2 +1 oxidizing agent 2° alcohol +2 -2 +1 ketone 2-propanol propanone (acetone) oxidizing agent 3° alcohol No reaction

Reaction of Alcohols with Hydrogen Halides 1° alcohols react via the SN2 reaction mechanism: C OH + HX C X + H2O 2° and 3° alcohols react via SN1 reaction mechanism: C C OH + HX C C X + H2O C C

Reaction of Alcohols with Hydrogen Halides CH3OH + HBr CH3Br + H2O CH3CHCH3 + HCl CH3CHCH3 + H2O OH Cl

Naming aldehydes and ketones Parent chain = longest chain containing C=O (carbonyl) Aldehyde Ketone Prefix Suffix Numbering oxo –e becomes –al C=O is always C #1 (don’t have to number it) oxo –e becomes –one C=O is lowest possible number (must number it) Naming Priority: Aldehydes > Ketones > Alcohols -OH (alcohol) substituent → “hydroxy” 3-hydroxy-4-methylpentanal 3-chloro-2-butanone

Has both an aldehyde and a ketone Naming Practice propanedial 2,4-pentanedione Aldehyde has priority Ketone = oxo Has both an aldehyde and a ketone 3-oxopentanal

Condensation of Alcohols Condensation reaction: two molecules combine to form a larger molecule (+ water) Catalyzed by acid (H+) H2SO4 catalyst CH3−OH + H-O−CH3 CH3−O−CH3 + H2O alcohol + alcohol ether + water

Two alkyl groups (C’s) bound to oxygen Ethers − H-bond acceptor No H-bond donor water alcohol Two alkyl groups (C’s) bound to oxygen Intermolecular forces: Dipole-dipole No H-bonding between ether molecules Lower boiling point than alcohols Water or alcohols can H-bond to ether oxygen Somewhat soluble in water and other polar solvents

Naming Ethers Common names: name both R groups, add “ether” diethyl ether (anesthetic) ethyl ethyl

tert-butyl methyl ether Naming Ethers Common names: name both R groups, add “ether” diethyl ether (anesthetic) ethyl ethyl tert-butyl methyl ether (used as gasoline additive) tert-butyl methyl propyl people ether propyl ♫ “one-eyed, one-horned, flying...” ♪

diisopropyl ether peroxide Reactions of Ethers Formation of peroxides peroxide + O2 diisopropyl ether Explosive! Reactions of peroxides: diisopropyl ether peroxide Controlled detonation Resulting crater: 3 feet wide, one foot deep

Aldehydes and Ketones C=O group called a carbonyl group C and O both sp2 hybridized 120° 120° aldehyde ketone C=O group called a carbonyl group − Very polar C=O bond Higher boiling point than alkanes H-bond acceptor Soluble in polar solvents No H-bond donor Lower boiling point than alcohols +

(contain a double bond) Structural Isomers Draw all the possible structural isomers for the following formulas: C4H10O C5H12O C4H8O C5H10O Alcohols and Ethers Aldehydes and Ketones (contain a double bond) Notice that all formulas contain one oxygen What functional groups do you know that contain one oxygen? Does the atom ratio of carbon to hydrogen make a difference?

isopropyl methyl ether C4H10O Isomers 1-butanol 2-butanol 2-methyl-2-propanol 2-methyl-1-propanol diethyl ether methyl propyl ether isopropyl methyl ether

C5H12O Isomers 1-pentanol 2-pentanol 3-pentanol 2-methyl-1-butanol 2,2-dimethyl-1-propanol

C5H12O Isomers butyl methyl ether tert-butyl methyl ether sec-butyl methyl ether isobutyl methyl ether ethyl propyl ether ethyl isopropyl ether

C4H8O Isomers butanal 2-butanone 2-methylpropanal

C5H10O Isomers pentanal 2-pentanone 3-pentanone 3-methylbutanal 3-methyl-2-butanone 2,2-dimethylpropanal 2-methylbutanal

Reactions of Aldehydes and Ketones Oxidation of aldehydes to carboxylic acids CrO3, MnO4- Reduction of aldehydes and ketones to alcohols Decrease C-O bonds, increase C-H bonds Reducing agents: LiAlH4, NaBH4, H2/Pt LiAlH4 propanal 1-propanol CH3−CH2−CHO CH3−CH2−CH2−OH NaBH4 2-methyl-3-pentanone 2-methyl-3-pentanol

Reduction of Aldehydes/Ketones LiAlH4 3-oxopentanal 1,3-pentanediol NaBH4 cyclohexanone cyclohexanol H2/Pt pentanedial 1,5-pentanediol

Carboxylic Acids Carboxyl group: -CO2H, -COOH − H-bond acceptor Carboxyl group: -CO2H, -COOH + − + H-bond donor Intermolecular forces: dipole-dipole, H-bonding Pure carboxylic acids form hydrogen bonded dimers very high boiling points (higher than alcohols)

Carboxylic Acid Nomenclature Parent chain: longest containing carboxyl group (COOH) Name of parent: replace “–e” with “–oic acid” Numbering starts at carboxyl carbon Priority: Carboxylic acid > aldehydes > ketones > alcohols  “hydroxy” substituent “oxo” substituents 3-oxobutanoic acid (diabetes) trans-3-methyl-2-hexenoic acid (human armpits) propanedioic acid (apples)

Can irritate your stomach aspirin Tylenol Can irritate your stomach Gentle on the stomach A carboxylic acid Just an alcohol

Carboxylic Acid Reactions Reduction to 1° alcohols Only LiAlH4 reduces carboxylic acids (not NaBH4 or H2/Pt) LiAlH4 butanoic acid 1-butanol NaBH4 butanoic acid NO RXN or H2/Pt Reactant remains unchanged

What are the products? 3-oxo-4-pentenoic acid 3-hydroxypentanoic acid H2/Pt NaBH4 LiAlH4 3-hydroxypentanoic acid 3-hydroxy-4-pentenoic acid 4-pentene-1,3-diol