13-1 Principles and Applications of Inorganic, Organic, and Biological Chemistry Denniston, Topping, and Caret 4 th ed Chapter 13 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Power Point to Accompany

13-2 Formulas Alcohols have the general formula R-OH Ethers have the formula R-O-R R can be aliphatic or aromatic Phenols have the formula Ar-OH Ar must be an aromatic ring (eg. Benzene) Thiols have the formula R-SH Disulfides have the formula R-S-S-R R may be aliphatic or aromatic

Alcohol: Structure and Properties Low molecular weight alcohols (up to 5-6 carbons) are soluble in water because they are polar and hydrogen bond (through the OH) with the water molecule. Eg. CH 3 CH 2 OH solube but CH 3 OCH 3 barely soluble. CH 3 CH 2 CH 2 CH 2 OH, 7 g per 100 mL but HOCH 2 CH 2 CH 2 CH 2 OH is very soluble! (two OH groups)

13-4 Alcohol Boiling Pts Alcohols have abnormally high bp relative to their molecular weights due to their ability to hydrogen bond.

13-5 Alcohol Boiling Pts-2 Trends in boiling points (Similar MW)

Alcohols: Nomenclature IUPAC: based on the longest chain containing the OH carbon. The e of the alkane name is replaced with ol. The chain is numbered from the end giving the OH carbon the lower number. The name is prefixed with the number indicating the position of the OH group. For cyclic alcohols, the OH is at C-1.

13-7 Alcohols: names-2 Name the alcohols. 3-methyl-2-butanol 3-methylcyclohexanol OH must be at C-1

13-8 Alcohols: names-3 The common names for alcohols consist of the alkyl group name, a space, and the word alcohol. Name: t-butyl alcohol isopropyl alcohol

Alcohol Examples of Interest

Classes of Alcohols Primary: one R group on alcohol C Secondary: Two R groups on alcohol C Tertiary: Three R groups on alcohol C

Reactions Involving Alcohols: prep 1. Form alkenes by adding water (hydration) Major Product

13-12 Alcohols Rxns: prep 2. Form aldehydes/ketones by reduction hydrogenation with H 2. 2o2o 1o1o

13-13 Alcohols: reactions 1. Alcohols dehydrate with heat and strong acid to give alkenes. Zaitsev’s rule (most substituted alkene) applies to determine the major product. Major product Minor product

13-14 Alcohols: reactions Zaitsev’s rule applied again H may leave from

13-15 Alcohols: reactions 2. Oxidation Secondary alcohols oxidize to ketones. (The reaction is also an elimination of 2H.) The usual oxidizing agent is a Cr(VI) species. Tertiary alcohols do not oxidize as there is no H on the carbonyl carbon to remove! 2H eliminated

13-16 Alcohols: reactions Primary alcohols usually oxidize to acids. With some care (Usually CrO 3 ) an aldehyde may be obtained. Easily oxidized to acid

Redox in Living Systems Oxidation-gain of oxygen loss of hydrogen (usually 2) Reduction-loss of oxygen gain of hydrogen (usually 2) More oxidized form More reduced form

13-18 Biological Redox-2 Oxidoreductases catalyze biological redox reactions. Coenzymes (organic molecules) are required to donate or accept hydrogen. NAD + is a common coenzyme.

Phenols Widely used as health care germicides and as flavors and preservatives. Thymol (mint)

Phenols-2 Phenols are acidic but not as acidic as carboxylic acids. They react with NaOH to give salts and water. (Acid/base chapter.) Note: alcohols are not acidic in the context of our class.

Ethers Ethers are slightly polar but do not hydrogen bond to one another. Trends in boiling points (Similar MW)

13-22 Ethers: names Common names for ethers consist of the names of the two groups attached to the O listed in alphabetical order (or size) and followed by ‘ether’. Each part is a separate word. Name: Isopropyl methyl ether ethyl phenyl ether

13-23 Ethers: names-2 The IUPAC names for ethers are based on the alkane name of the longest chain attached to the O. The shorter chain is named as an alkoxy substituent. (alkane with the ane replaced by oxy, eg. CH 3 CH 2 O=ethoxy) Thus CH 3 CH 2 CH 2 CH 2 CH 2 -O-CH 3 1-methoxypentane

13-24 Ethers: reactions Chemically ethers are moderately inert Symmetrical ethers may be prepared by dehydrating two alcohol molecules

13-25 Ethers: uses Ethers are often used as anesthetics. Diethyl ether First successful general anesthetic penthrane

Thiols: names Named based on longest alkane chain with the suffix thiol position indicated by number. E. g. 3-methy-1-butanethiol

13-27 Thiols/Disulfides: reactions The thiol-disulfide redox pair is responsible for a critical factor in protein structure called a disulfide bridge.

13-28 The End Alcohols, etc.