Dr A.K.M. Shafiqul Islam University Malaysia Perlis

Alcohols and ethers are organic derivatives of water where one or both H atoms are replaced by R groups. H-O-H  R-O-H  R-O-R’ AlcoholEther Water

Alcohols Functional group is -OH, the hydroxyl group, bonded to a tetrahedral carbon Nomenclature Rules –Same as for Alkenes and Alkynes except you only drop the -e, and add -ol! propanepropanol

Nomenclature of Alcohols 1) Select the longest chain that contains the carbon bonded to the -OH group, and number the chain to give the carbon bonded to the -OH group the lowest number The -OH group takes precedence over alkyl groups, double bonds, triple bonds, and halogens!!!

Nomenclature of Alcohols 2) Change the suffix by dropping the -e, and adding -ol. Use the number to show location. In cycloalkanes, start numbering from the carbon bonded to the -OH. 3) Name and number substituents and list them in alphabetical order.

Naming Alcohols 1. The parent chain must contain the –OH group. Change parent ending to “-ol”. 2. Give the –OH the lowest possible number. 6,6-dimethyl-3-heptanol

Alcohol Nomenclature methanol methyl alcohol 1º ethanol ethyl alcohol 2º 2-propanol isopropyl alcohol 3º 2-methyl-2-propanol tert-butyl alcohol

4-methyl-2-pentanol 4-chloro-2-methyl-2-pentanol 2,6-dichloro-4-methyl-4-octanol OH > C=C > R, X

4-penten-2-ol 5-chloro-3-hexen-2-ol OH > C=C > R, X 3-chloro-2-ethyl-2-buten-1-ol

A) 2,3-diethyl-5,5-dimethyl-2-hexanol B) 4,5-diethyl-2,2-dimethyl-5-hexanol C) 4-ethyl-3,6,6-trimethyl-3-heptanol D) 4-ethyl-2,2,5-trimethyl-5-heptanol E) 1,2-diethyl-1,4,4,-trimethyl-1-pentanol What is the systematic name for this alcohol?

Naming Alcohols 3. When the –OH group is attached to a ring, it is assumed to be at carbon #1. 2-methylcyclopentanol (NOT 2-methyl-1-cyclopentanol)

A) 7-ethyl-3,3-dimethylcycloheptanol B) 2-ethyl-6,6-dimethyl-1-cycloheptanol C) 4-ethyl-1,1-dimethylcycloheptanol D) 2-ethyl-6,6-dimethylcycloheptanol E) 7-ethyl-3-dimethylcycloheptanol What is the systematic name for this alcohol?

Classification We classify alcohols as 1 o, 2 o, and 3 o, depending on the classification of the carbon they are bonded to.

Multiple -OH’s present Molecules with 2 -OH’s are named as diols Molecules with 3 -OH’s are named as triols (Note: you do not drop the -e when using diol, triol, etc) Compounds with 2 -OH’s are refered to as glycols

Physical Properties of Alcohols The most important physical property is their polarity Both the C-O bond and the O-H bond are polar covalent bonds Thus alcohols are polar molecules They also have the ability to hydrogen bond. These factors lead to higher B.P’s, M.P’s. etc

Physical Properties of Alcohols Because of increase London forces (van der Waals forces) between larger molecules, the B.P. of all types of compounds, including alcohols, increase as molecular weight increases Alcohols are much more soluble in H 2 O due to their H-bonding capacity. As MW increases, the water solubility of alcohols decreases This is because the hydrocarbon portion of the molecule dominates.

Reactions of Alcohols A)Acidity of Alcohols -Alcohols are considerably weaker acids than carboxylic acids, but can lose their hydrogen in an acid-base reaction.

Methanol Methanol was once prepared by the destructive distillation of wood. Wood alcohol. Toxic, causes blindness in low doses (15 mL). Routinely used as a solvent and starting material. Methanol used by the chemical industry is prepared by the catalytic reduction of carbon monoxide. CO + 2 H 2 CH 3 OH 250°C Cu/ZnO/Al 2 O 3

Ethanol Prepared by the fermentation of grains and sugars. Grain alcohol. Used in alcoholic beverages. The largest single use of ethanol is as a motor fuel and fuel additive (replaces MTBE). 5 billion gallons are prepared (primarily from corn) annually in the U.S. for fuel uses. H 2 C=CH 2 + H 2 O CH 3 CH 2 OH 250°C H 3 PO 4 Ethanol used by the chemical industry is prepared by the acid-catalyzed hydration of ethylene.

The Polar -OH Group The physical properties of the alcohols are strongly influenced by the polar -OH group. Methanol Electrostatic Potential Map Negatively polarized oxygen Positively polarized hydrogen Neutral methyl group

CH 3 CH 2 CH 2 OH CH 3 CH 2 Cl CH 3 CH 2 CH 2 CH 3 CompoundMW (g/mol)BP (°C) Boiling Points The polar -OH group allows hydrogen bonding to take place in alcohols. These strong intermolecular forces result in higher than expected boiling points. -- -- -- -- -- ++ ++ ++ ++ +

Structure- functional group is a Oxygen bonded to 2 carbons Simplest ether is dimethyl ether Ethers

Nomenclature of Ethers The common naming system is used for simple ethers: –List the alkyl groups bonded to the oxygen in alphabetical order, followed by the work “ether”.

Ether Nomenclature diethyl ether cyclohexyl methyl ether cyclooctyl ethyl ether ethyl methyl ether

Crown Ethers Large rings consisting repeating (-OCH 2 CH 2 -) or similar units Named as x-crown-y –x is the total number of atoms in the ring –y is the number of oxygen atoms –18-crown-6 ether: 18-membered ring containing 6 oxygens atoms Central cavity is electronegative and attracts cations

18-Crown-6

Uses of Crown Ethers Complexes between crown ethers and ionic salts are soluble in nonpolar organic solvents Creates reagents that are free of water that have useful properties Inorganic salts dissolve in organic solvents leaving the anion unassociated, enhancing reactivity

Physical Properties of Ethers Ethers are polar compounds The oxygen has a partial minus charge, the carbons bonded to the oxygen have a partial positive charge Ether have very weak intermolecular forces which results in low boiling points

The Ethers Diethyl ether Electrostatic Potential Map Neutral ethyl group Negatively polarized oxygen Ethers lack the polar -OH group and therefore do not have hydrogen bonding. Neutral ethyl group

Reactions of Ethers Like alkanes, they are resistant to most chemical reactions Therefore, they are ideal to use as solvents

Diethyl Ether Was once widely used as an anesthetic. Highly flammable. Presently used as a solvent. 2 CH 3 CH 2 OH CH 3 CH 2 OCH 2 CH 3 + H 2 O H 2 SO 4 Prepared by the sulfuric acid-catalyzed dehydration of ethanol.

CH 3 CH 2 CH 2 CH 2 OH CH 3 OCH 3 Compound MW (g/mol)BP (°C) CH 3 CH 2 OH CH 3 CH 2 OCH 2 CH 3 Boiling Points Ethers have weak intermolecular forces, which results in low boiling points. Low molecular weight ethers are highly volatile

ROR’ ROH CompoundBPPolarity Hydrogen- Bonding? Reactive?Uses Alcohols & Ethers polaryes starting materials non- polar no high low yes nosolvents Alcohols and ethers have very different chemical and physical properties. This is due to the polar -OH group that’s present in alcohols but absent in ethers.

Oxidation and Reduction Carboxylic Acid Aldehyde / Ketone Alcohol Alkane Oxidation: Increase C-O bonds Reduction: Increase C-H bonds OXIDATIONOXIDATION REDUCTIONREDUCTION

Common Reducing Agents Sodium borohydride (NaBH 4 ) is a mild reducing agent. aldehyde 1º alcohol ketone 2º alcohol

Lithium aluminum hydride (LiAlH 4 ) is a strong reducing agent. carboxylic acid 1º alcohol Common Reducing Agents

Predict the Products

Common Oxidizing Agents Pyridinium chlorochromate (PCC) (C 5 H 6 NCrO 3 Cl) is a mild oxidizing agent. 1º alcohol aldehyde 2º alcohol ketone

Chromium trioxide (CrO 3 ) and sodium dichromate (Na 2 Cr 2 O 7 ) are strong oxidizing agents. 1º alcohol carboxylic acid 2º alcohol ketone Common Oxidizing Agents

Predict the Products

The Williamson Ether Synthesis RO - + R’X  ROR’ + X - alkoxidealkyl halide ether SN2SN2 R can be 1º, 2º, 3º, or cycloalkyl. R’ should be methyl or 1º. R can be 1º, 2º, 3º, or cycloalkyl. R’ should be methyl or 1º. 2 ROH + 2 M  2 ROM + H 2 alcoholM = Na, K

CH 3 CH 2 O - + CH 3 CH 2 I  CH 3 CH 2 OCH 2 CH 3 + I - ethoxide ion ethyl iodide diethyl ether SN2SN2 Diethyl ether is a symmetrical ether. 2 CH 3 CH 2 OH + 2 Na  2 CH 3 CH 2 ONa + H 2 ethanolsodium ethoxide Synthesis of Diethyl Ether via the Williamson Synthesis

Synthesis of tert-Butyl Methyl Ether via the Williamson Synthesis + S N 2 nucleophiletert-butyl methyl ether This is the better route base E methylpropene tert-Butyl methyl ether is an asymmetrical ether.