Alcohols, Phenols and Ethers Chem 1152: Ch. 13 Alcohols, Phenols and Ethers

Introduction alcohol ether Alcohol: Any cmpd with a hydroxy (-OH) functional group attached on aliphatic carbon. Phenol: Hydroxy functional group attached to benzene ring, where the parent is a combination of the benzene ring and the (-OH) group. Ether: Oxygen with carbon attached on either side. Water structure analogs to alcohol and ether alcohol ether

Classification of Alcohols Primary (1°) Hydroxy bearing C is attached to either 0 or 1 other C Secondary (2°) Hydroxy bearing C is attached to 2 other C Tertiary (3°) Hydroxy bearing C is attached to 3 other C

Examples of Alcohols Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Examples of Alcohols Antifreezes 1,2-ethanediol (ethylene glycol) 1,2-propanediol (propylene glycol) Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Rules for naming alcohols For single hydroxy (-OH) group Step 1: Identify longest chain that includes (-OH) group. Drop –e from hydrocarbon name, and replace with ending –ol. Step 2: Number this parent chain to give lowest number to carbon with attached (-OH) group. Step 3: Locate position of (-OH) group. Step 4: Locate and name all branches attached to parent chain. Step 5: Include names of all branches (still in alphabetical order) in prefix of compound name. Include location of (-OH) group. Note: Multiple (-OH) groups are named by addiing diol, triol, etc, to end of alkane without removing -e. 1 2 3 4 2 5 1 4 3 2-ethyl-1-pentanol 2-methyl-1,4-butanediol

Naming Alcohols

Naming Alcohols 2,2,4-trimethyl-3-hexanol 5-bromo-3-ethyl-1-pentanol 1,2,4-hexanetriol 3-butyl-2,4-hexanediol 2,2-dimethylcyclopentanol 3-methyl-3-pentanol 1,2-cyclohexanediol 2-isopropyl-1-methylcyclopropanol 3-phenyl-1-propanol

Physical Properties of alcohols- Solubility Low MW alcohols (methanol, ethanol, propanol) are miscible with water. As alkane chain gets longer, alcohol behaves more like an alkane: More soluble in nonpolar organic solvents (benzene, CCl4, ether) Alcohols that look like water, behave like water. Alcohols that look more like alkanes behave like alkanes. Due to hydrogen bonding. Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Hydrogen bonding Hydrogen bond: Attractive interaction of a hydrogen atom with an electronegative atom (e.g. N, O, F) from another molecule or chemical group. The H must be covalently bonded to another electronegative atom. This is why H on hydrocarbon chain does not participate in H-bonding. H-bond relatively weak. Bond energy for C-H 413 kJ/mol H-bond energy 2 kJ/mol Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Effects of hydrogen bonding H-bonding between alcohol molecules increases BP for alcohol compared to similar MW alkane Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Alcohol Dehydration (Elimination Rxn): Alcohol Reactions Alcohol Dehydration (Elimination Rxn): Alcohol Hydration (Addition Rxn)

Alcohol Dehydration to produce alkene Alcohol Dehydration (Elimination Rxn): 2-butene 1-butene This rxn (at 180 °C) generates 2 products: 2-butene and 1-butene. The major product is 2-butene (90%) because both C=C bond carbons are attached to at least one other carbon. The minor product is 1-butene (10%) because only one of the C=C bond carbons is attached to at least one other carbon. The major product in these rxns will always be the one resulting in the highest number of carbon groups bonded to the C=C carbons.

Alcohol dehydration in biochemistry citrate cis-aconitrate This rxn is catalyzed by an enzyme rather than an acid in the human body. Alcohol dehydration rxns in general are involved in the formation of: Carbohydrates Fats Proteins

Examples: Alcohol Dehydration to Produce Alkene

Alcohol Dehydration to produce ether Alcohol Dehydration (Elimination Rxn): alcohol alcohol ether This rxn (at 140 °C) generates an ether and water. This rxn works mainly with primary alcohols. Primary (1°) Hydroxy bearing C is attached to either 0 or 1 other C

Alcohol Oxidation Oxidation: Loss of hydrogen or gain of oxygen. Oxidizing Agent: Compound that oxidizes another compound. KMnO4 (potassium permanganate) K2Cr2O7 (potassium dichromate) This rxn works different depending on whether alcohol is 1°, 2° or 3°. H-OH lost in oxidation rxns comes from the same carbon, rather than adjacent carbons as seen in dehydration rxns to form alkenes.

Alcohol Oxidation for Primary Alcohol aldehyde Primary alcohol Carboxylic acid Immediate product of oxidation of primary alcohol is aldehyde, which is then readily further oxidized to a carboxylic acid. The aldehyde product may be isolated before further oxidation by maintaining high temp. and boiling aldehyde out of rxn mixture. This is possible because aldehydes do not H-bond like alcohols and carboxylic acids.

Alcohol Oxidation for Secondary and Tertiary Alcohols Secondary alcohol ketone Product of oxidation of secondary alcohol is a ketone, which resists further oxidation. Tertiary alcohol

Examples: Identify Rxn and draw product

Examples: Identify Rxn and Draw Product

Summary of Alcohol Reactions Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Phenols Phenol: Hydroxy functional group attached to benzene ring, where the parent is a combination of the benzene ring and the (-OH) group. Low MP solid that liquefies at room temp. with small amount of water. Weakly acidic in water (due to conjugated pi bonds on benzene ring). Can damage proteins in skin. In dilute solutions, can be used as antiseptics and disinfectants. Phenol first used by Joseph Lister in hospitals in 1800’s. Phenol derivatives used today in Lysol, mouthwashes and throat lozenges. Other phenol derivatives used as antioxidants.

Naming Phenols Substituted phenols are usually named as derivatives of the parent compound phenol. Examples: Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Ethers Ether: Oxygen with carbon attached on either side. Naming ethers Common Names Name the two groups attached to the oxygen then add the word ether If both groups the same, can be named with prefix di-. IUPAC Names O-R group is alkoxy. The –yl ending of smaller R group is replaced by –oxy. butyl methyl ether 1-methoxybutane isopropyl propyl ether 1-isopropoxypropane p-methoxytoluene ethyl propyl ether 1-ethoxypropane dipropyl ether 2-ethoxy-3,4-dimethylhexane 2-chloro-1-isopropoxypropane 1-propoxypropane

Properties of Ethers Oxygen atom of ether can H-bond with water Ethers more soluble in water than hydrocarbons, less soluble than alcohols of comparable MW. Ethers cannot H-bond with other ethers in pure state Results in low BP close to those of hydrocarbons of comparable MW. Ethers mostly inert and unreactive Why diethyl ether is useful solvent Diethyl ether is also highly-flammable and was historically an important anesthetic History Note: First physician to use diethyl ether as anesthesia was Crawford Long in 1842 Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

2-methyl-3-hexanethiol Thiols Thiols: Sulfur analogs of alcohols (-SH instead of –OH) Chemically- similar (i.e., form similar compounds) More volatile (lower BP) than alcohols but less water-soluble Thiols stink! This is how skunks defend themselves Chopped onions emit propanethiol Thiols found in garlic Ethanethiol added to natural gas (methane) so you can smell a leak IUPAC Names for simple thiols The –SH group is a sulfhydryl group. Follow the same steps for naming as you do for alcohols, but do not modify alkane ending; instead add –thiol to end of parent. butanethiol 2-butanethiol 2-methyl-3-hexanethiol

Thiol/Sulfide Rxns Oxidation (Formation of disulfide bond) Reduction (breaking disulfide bond)

Polyfunctional Compounds Substances that can contain more than 1 functional group. Ribose forms backbone of RNA (genetic transcription). Phosphorylated ribose becomes subunits of ATP, NADH, and several other compounds that are critical to metabolism. http://www.daviddarling.info/encyclopedia/R/ribose.html http://en.wikipedia.org/wiki/RNA

Multistep Rxns The synthesis of most alcohols may require multiple steps (i.e., to get product X from reactant A, a product (B, C …X) must be created). To solve these problems, work backwards from the final product. Oxidize 2° alcohol to form ketone. Use acid-catalyzed hydration (addition) to form alcohol. The completed series of rxns.