Chapter 14 & 15 Alcohols, Ethers, Thiols and Chirality

1. Chemistry B11 Chapter 14 & 15 Alcohols, Ethers, Thiols and Chirality

2. OH Alcohols Alcohols Contain a hydroxyl group (-OH). Phenols Contain a benzene ring with a hydroxyl group (-OH).

3. Naming Alcohols • IUPACname: We replace the -e in alkane name with -ol. • Common name: As simple alcohols using the name of the alkyl group followed by “alcohol”. • CH4 methane • CH3─OH methanol (methyl alcohol) • CH3─CH3 ethane • CH3─CH2─OH ethanol (ethyl alcohol)

4. Naming Alcohols Step 1 Select the longest carbon chain that contains the -OH group. Step 2 Number from the end nearest -OH group. Step 3 Change the ending of parent alkane from -e to -ol. Use the number to show the location of -OH. Step 4 Give the location and name of each substituent (alphabetical order) as a prefix to the name of the main chain.

5. Naming Alcohols CH3─CH2─CH2─OH 1-propanol OH │ CH3─CH─CH3 2-propanol CH3 OH │ │ CH3─CH─CH2─CH2─CH─CH3 5-methyl-2-hexanol 1 2 3 3 2 1 5 6 4 3 2 1

6. Naming Alcohols OH │ CH3─CH─CH2─CH3 2-butanol CH3 │ CH3─CH─CH─CH2─OH 3-chloro-2-methyl-1-butanol CH3 CH3─C─CH2─OH 2,2-dimethyl-1-propanol 1 2 3 4 Cl 4 3 2 1 CH3 3 2 1

7. Diols & Triols Diol:a compound containing two –OH (Hydroxyl groups). Triol:a compound containing three –OH (Hydroxyl groups). CH2 – CH2 CH2 – CH – CH2 CH3 – CH – CH2 OH OH OH OH OH OH OH 1,2-Ethanediol (Ethylene glycol) 1,2-Propanediol (Propylene glycol) 1,2,3-Propanetriol (glycerol, glycerin)

8. Different types of Alcohols Primary (1º) Secondary (2º ) Tertiary (3º) H CH3 CH3 │ │ │ CH3─C─OH CH3─C─OH CH3─C─OH │ │ │ H H CH3 1 C 2 C 3 C attached attached attached to C-OH to C-OH to C-OH

9. Phenol • Phenol is the IUPAC name for benzene with a hydroxyl group. • Many are used as antiseptics and disinfectants. • Is a weak acid. OH Phenol

10. OH Physical Properties of Alcohols • Alcohols are polar molecules (because of O-H and C-O). • Hydrogen bonding between alcohols molecules. • Have higher boiling points than Alkanes, Alkenes, and Alkynes. • Molecular weight ↑ : London dispersion forces ↑ : bp ↑ • More soluble in water (Molecular weight ↑ : solubility ↓). • They are weak acids (weaker than Phenol). C-O: (3.5 – 2.5 = 1.0) O-H : (3.5 – 2.1 = 1.4) polar nonpolar

11. Chemical Properties of Alcohols 1. Acidity of Alcohols: 2. Acid-Catalyzed Dehydration: H2SO4 CH3CH2OH CH2 = CH2 + H2O 180°C Dehydration - C – C - C = C + H20 Hydration H OH 3. Oxidation of Alcohols:

12. Oxidation of 1° Alcohols In the oxidation [O] of a primary alcohol 1, one H is removed from the –OH group and another H from the C bonded to the –OH. primary alcohol aldehyde OH O │ ║ CH3─C─H CH3─C─H + H2O │ H ethanol ethanal (ethyl alcohol) (acetaldehyde) [O] K2Cr2O7 H2SO4

13. Oxidation of 2° Alcohols The oxidation of 2 alcohols is similar to 1°, except that a ketone is formed. secondary alcohol ketone OH O │ ║ CH3─C─CH3 CH3─C─CH3 + H2O │ H 2-propanol 2-propanone [O] K2Cr2O7 H2SO4

14. Oxidation of 3° Alcohols Tertiary 3 alcohols cannot be oxidized. Tertiary alcohol no reaction OH │ CH3─C─CH3 no product │ CH3 no H on the C-OH to oxidize 2-methyl-2-propanol [O] K2Cr2O7 H2SO4

15. Oxidation of Alcohols in our body • In the body: • Enzymes in the liver oxidize ethanol. • Blood alcohol over 0.4% can be fatal. • O O • ║║ • CH3CH2OH CH3CH CH3COH 2CO2 + H2O + Energy • ethanol ethanal acetic acid [O] [O] [O]

16. Ethers

17. Ethers • An ether: • Contains an -O- between two carbon atoms. • Is named from alkyl names of the attached groups • (in alphabetical order) followed by ether. • CH3─O─CH3 CH3─CH2─O─CH3 • dimethyl ether ethyl methyl ether

18. δ+ δ+ δ+ δ- Physical Properties of Ethers • They are polar compounds (because of C-O). • Weak dipole-dipole interactions. • Low boiling points: hydrocarbons < ethers < alcohols. • More soluble in water than other hydrocarbons • of similar molecular weight (H-bond with water). C-O (3.5 – 2.5 = 1) H O δ+ H δ-

19. Chemical Properties of Ethers Ethers are resistant to chemical reactions (inert). Oxidation Reduction Good solvent for organic reactions.

20. Thiols

21. Thiols • An Thiol: • Contains an –SH (sulfhydryl) group. • Is named by selecting the longest carbon chain that contain the -SH. We add -thiol to the name of the parent alkane. • Parent chain is numbered from the end nearest to • the -SH group. • CH3─S─H CH3─CH2─S─H • Methanethiol Ethanethiol

22. Naming Thiols Step 1 Select the longest carbon chain that contains the -SH group. Step 2 Number from the end nearest -SH group. Step 3 Add –thiol to the name of the parent alkane. Use the number to show the location of -SH. Step 4 Give the location and name of each substituent (alphabetical order) as a prefix to the name of the main chain.

23. CH3 CH3CHCH2CH2CH2SH 4-Methyl-1-pentanethiol 5 4 3 2 1 CH3 CH3CHCH2SH 2-Methyl-1-propanethiol 2 1 3 Cl SH CH3 CH3-CH-CH2-CH-CH-CH3 5-Chloro-3-methyl-2-hexanethiol 1 5 4 2 3 6

24. Physical Properties of Thiols • They have unpleasant odors. • They are nonpolar compounds. • S-H (2.5 – 2.1 = 0.4) nonpolar covalent. • 3. Low boiling points (London dispersion forces). • 4. Almost insoluble in water.

25. Chemical Properties of Thiols 1. Thiols are weak acids (react with strong bases). H2O CH3CH2SH + NaOH CH3CH2S-Na+ + H2O Sodium ethanethiolate 2. Oxidation to disulfides: -S-S- disulfide Oxidation 2OHCH3CH2SH + O2 HOCH2CH2S-SCH2CH2OH Reduction

26. Chirality

27. Isomers same different connectivity connectivity Constitutional Isomers Stereoisomers without with stereocenters stereocenters Cis-Trans Isomers Chiral Achiral Enantiomers Diastereomers

28. A

29. Achiral superposable mirror images 2-propanol This means that the original and its mirror image are the similar molecules.

30. Enantiomers (chiral) nonsuperposable mirror images 2-butanol They have different chemical and physical properties.

31. stereocenter A carbon with four different groups bonded to it. It usually creates enantiomers.