Phenols, Ethers, and Organic Sulfur Compound

Transcription

1 Phenols, Ethers, and rganic Sulfur Compound

2 Phenols - Structure General Structure - A hydroxy () group attached directly to an aromatic ring: Phenol α-naphthol β-naphthol Note: CH2 is not a phenol.

3 Phenols - Nomenclature Phenols are named as aromatic compounds, using the ortho-, meta-, and para- prefixes or appropriate numbering. 1 N nitrophenol or ortho-nitrophenol Cl 3-chlorophenol or meta-chlorophenol CH3 4-methylphenol or para-methylphenol 1 Br 1 2,4-dibromophenol Br 2 Cl Br 4-bromo-2-chloro-5-isopropyl-phenol

4 Phenols - Physical Properties Low Melting Solids Soluble in Nonpolar Solvents Also, Quite soluble in Water Name Phenol Catechol Resorcinol M.P ºC 105 ºC 110 ºC Solubility 8.3 g/100ml 43 g/100ml 110 g/100ml in water

5 Phenols - Acidity In water, phenol dissociates slightly as a weak acid. (Another name for phenol itself is carbolic acid ) _ + H2 + H3 + Acid Base Base Acid

6 Phenols - Acidity

7 Phenols - Acidity How acidic is Phenol? pka = A general measure of acidity. The lower the pka, the stronger the acid. Compound pka nonacids weak acids strong acids Methanol 16 Water 15.7 Phenol 9.9 Acetic Acid 4.8 Phosphoric Acid -2.1 Hydrochloric Acid -7

8 Acidity of Alcohols

9 Phenols - Chemical Properties Acid-Base Reactions - Na + + Na + H Phenol Sodium phenoxide

10 6. Complete the following reaction and name the organic reactant and product. N 2 Na + H2 4-methyl-3-nitro phenol C7H63NNa

11 7. Review: What structural feature is present in some alcohols which enables the molecules to undergo intramolecular dehydration? H C C 8. Review: What structural feature is present in some alcohols which enables the molecules to undergo oxidation? H C 9. Review: What structural feature is present in alcohols which enables the molecules to undergo a reaction with sodium (Na) metal? H C 10. Review: What structural feature is present in a specific class of alcohols which enables the molecule to undergo a reaction with aqueous Na?

12 Phenols - Chemical Properties Acid-Base Reactions - Na + + Na + H xidation- Reduction Reactions Phenol XIDATIN Sodium phenoxide + 2 H. Hydroquinone REDUCTIN Paraquinone

13 Phenols - Examples of Important Compounds CH2CH2CH2CH2CH2CH3 o-phenyl phenol 4-hexylresorcinol butylated hydroxy anisole (BHA) CH3 butylated hydroxy toluene (BHT)

14 Structure of Ethers

15 Structure of Ethers

16 Chemical Properties of Alcohols Intermolecular Dehydration Reactions H H H C C H H H+ H H H H H + H C C H H C C C C H + H 2 H H H H H H H H + + C2H6 C2H6 C4H10 H2 2 molecules of ethanol H and on two different molecules The reaction is run under different conditions than the intramolecular dehydration. diethyl ether Also called condensation or dehydration synthesis - an extremely important reaction in biochemistry.

17 Nomenclature of Ethers Common Nomenclature For simple carbon groups, the two groups attached to the ether oxygen are named as alkyl groups and ether is added to the name. ethyl methyl ether diethyl ether ethyl phenyl ether

18 Nomenclature of Ethers IUPAC System Shorter carbon chains are named as alkoxy- groups. Br F Cl CH 1-chloro-3-methoxypentane 2-bromo-4-ethoxy-1-fluorobenzene

19 Nomenclature of Ethers A compound may contain two functional groups, in which case priorities are assigned.

20 Important Anaesthetics

21 Physical Properties of Ethers Boiling points of ethers increase with molecular weight and decrease with increased branching

22 Physical Properties of Ethers Attractive forces between ether molecules include only dispersion forces making their boiling points similar to alkanes of similar molecular weight. Hexane, boiling point 69 C Butyl methyl ether, boiling point 71 C H H H H H 1-Pentanol, boiling point 138 C

23 Physical Properties of Ethers The solubility of a compound in water is related to the ability of water molecules to overcome the attractive forces between two potential solute molecules. CH2 CH2 CH2 CH2 Hexane, insoluble in water CH2 CH2 CH2 CH2 1-pentanol, slightly soluble in water

24 Physical Properties of Ethers The ether oxygen can hydrogen bond with water. The result is some water solubility. CH2 CH2 1-methoxybutane, slightly soluble in water 1,2-dimethoxyethane, very soluble in water

25 As a general rule, one polar atom (,N) can solubilize four to six carbon atoms.

26 rganic Sulfur Compounds Structures R-S-H Thiols (Mercaptans) R-S-R Thioethers (Sulfides) R-S-S-R (Disulfides) Nomenclature CH3-S-H CH3-S-CH3 CH3-S-S-CH3 Mercaptan (Methanethiol) Dimethyl Sulfide (Dimethyl Thioether) Dimethyl disulfide Physical Properties Distinct odors and flavors Lower boiling points than alcohols (Why?) Weak Acids: Phenols > Thiols > Alcohols

27 rganic Sulfur Compounds Chemical Properties Thiols are easily oxidized to disulfides and Disulfides are easily reduced to thiols. This reaction takes place within large protein structures: H-S S-H xidation Reduction S S

28 rganic Sulfur Compounds Chemical Properties Mercaptans = Mercury capturing R-SH R-S Hg 2+ Hg + 2 H+ R-SH R-S Process is called chelation

29 Where Do We Find Thiols??

30 Where Do We Find Disulfides??