Presentation is loading. Please wait.

Presentation is loading. Please wait.

Alcohols Contain a hydroxyl (-OH) group

Similar presentations

Presentation on theme: "Alcohols Contain a hydroxyl (-OH) group"— Presentation transcript:

1 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

2 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

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

4 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

5 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

6 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 +

7 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)

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

9 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+

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

11 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)

12 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

13 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

14 Reaction of Alcohols with Hydrogen Halides



17 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

18 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

19 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

20 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

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

22 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...” ♪



25 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

26 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 +

27 (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?

28 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

29 C5H12O Isomers 1-pentanol 2-pentanol 3-pentanol 2-methyl-1-butanol

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

31 C4H8O Isomers butanal 2-butanone 2-methylpropanal

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

33 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

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

35 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)

36 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)

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

38 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

39 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

Download ppt "Alcohols Contain a hydroxyl (-OH) group"

Similar presentations

Ads by Google