Ch. 23 Functional Groups

23.1 Introduction to Functional Groups Most organic chemistry involves substituents that contain oxygen, nitrogen, sulfur, and/or phosphorus Functional Groups chemically functional part of the molecule a specific arrangement of atoms in a compound that is capable of characteristic chemical reactions

Halocarbons Contains at least one fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) atom Naming based on IUPAC rules for the name of the parent hydrocarbon

Substitution Reactions One atom or group of atoms replaces another atom or group of atoms Important method for introducing a new functional group to an organic molecule Ex. In general for a halogen substitution (halogenation) reaction Ex. Reaction of methane with chlorine

Substitution Reactions Halocarbons can be used to prepare alcohols Fluorine is more difficult to displace (generally not used for this purpose)

23.2 Alcohols, Ethers, and Amines Alcohols: organic compounds with an –OH group (hydroxyl group) IUPAC naming: drop the –e ending from the parent hydrocarbon and add –ol Specify which C the –OH group is on with a number before the name If multiple –OH groups, add number prefix to the –ol ending (ex. Butanol, butanediol, butanetriol)

Properties of Alcohols Capable of hydrogen bonding (intermolecular) Somewhat soluble in water Up to 4C alcohols are completely soluble in water Longer hydrocarbon chains are not soluble because they are mostly nonpolar

Uses of Alcohols 2-propanol 1,2,3-propanetriol 1,2-ethanediol Ethanol Antiseptic Base for perfumes, creams, lotions, other cosmetics 1,2,3-propanetriol Absorbs water from surroundings, used as a moistening agent in cosmetics, food, and pharmaceuticals 1,2-ethanediol antifreeze Ethanol Industrial uses (methanol added to “denature”)

Fermentation Production of ethanol from sugars by yeast or bacteria Used to produce ethanol for alcoholic beverages *depressant, fatal in large doses

Addition Reactions A substance is added at a double or triple bond Important method for introducing a new functional group to an organic molecule Convert alkenes to alkanes

Hydration Reactions Water is added to an alkene (H + OH) Forms an alcohol Occurs under heat (100⁰C)

Halogenation Reactions Adds 1 or 2 halogens to an alkene or alkyne Ex. Bromine has an orange color, but most unsaturated compounds form colorless halogenated compounds, so bromine is used to test whether a substance is saturated or not

Hydrogenation Reactions

Ethers General formula: ROR Naming: identify the two R groups (hydrocarbons), put in alphabetical order, and add ether to the end

Ethers Diethyl ether was the first reliable general anesthetic Highly flammable and often causes nausea Diphenyl ether is used in soaps and perfumes (geranium smell) Boiling points between those of alcohols and hydrocarbons Less soluble in water than alcohols fewer hydrogen bonds

Amines Contain nitrogen (N) bonded to a carbon group Similar to ammonia (NH3) General formulas: RNH2, R2NH, or R3N IUPAC naming: drop –e ending of parent hydrocarbon and add –amine Hydrogen bonding is weaker than that of alcohols (N is less electronegative than O)

Amines Used in some dyes such as methyl orange (also used as an indicator)

23.3 Carbonyl Compounds Carbonyl group: general structure C=O Aldehyde: carbon of the carbonyl group is bonded to at least one hydrogen Ketone: carbon of the carbonyl group is attached to two other carbons

Aldehydes IUPAC naming: identify and name the longest carbon chain that includes the carbonyl group (C=O), replace the –e ending of the parent hydrocarbon with –al Most commonly used: methanal (formaldehyde) making synthetic resins Preserving biological specimens Aromatic aldehydes produce scents/flavors ex. almond, vanilla, cinnamon

Ketones IUPAC naming: identify and name the longest carbon chain that includes the carbonyl group, change –e ending to –one, designate the carbonyl carbon with the lowest possible number Most commonly used: propanone (acetone) Solvent for resins, plastics, varnishes Nail-polish remover

Properties of Aldehydes and Ketones No hydrogen bonding between aldehyde or ketone molecules (but weak H-bonds with water) Weak polar attractions between carbonyl groups Soluble in non-polar solvents Smaller compounds are soluble in water

Carboxylic Acids Carboxyl group: carbonyl group bonded to a hydroxyl group (-COOH) Carboxylic acid: organic compound with a carboxyl group General formula: RCOOH Weak acid (see below) IUPAC naming: replace –e of parent hydrocarbon with –oic acid Parent hydrocarbon number includes the carbon of the carboxyl group

Carboxylic Acids Abundant in nature Citric acid = 2-hydroxypropane-1,2,3-tricarboxylic acid Vinegar = acetic acid (acetum is Latin for vinegar) Fatty acids: first isolated from fats

Esters Contain a carbonyl group and an ether link to the carbonyl carbon General formula: RCOOR Contribute characteristic odors to many fruits and perfumes Neutral substances, cannot form H-bonds with other esters Can be prepared from a carboxylic acid and an alcohol

Esters heated in water do very little, but in presence of acid or base the ester breaks down rapidly

23.4 Polymers Polymer: a large molecule of repeating smaller molecules covalently bonded together Monomer: smaller molecules that join to form a polymer

Addition Polymers Form when unsaturated monomers react to form a polymer Require monomers with double bonds Often requires a catalyst to get the reaction started Length of carbon chains can change properties

Addition Polymer Examples Polypropylene: stiffer plastic used for utensils and drink containers Polystyrene: good insulator

Addition Polymer Examples Polyvinyl chloride (PVC): pipes to upholstery covering Polytetrafluoroethene (PTFE): heat and corrosion resistant, nonstick, aka Teflon Polyisoprene: rubber

Condensation Polymers Formed by the joining of monomers with the loss of a small molecule such as water Polyesters: monomers of dicarboxylic acids and dihydroxy alcohols joined by ester bonds Must have two functional groups on each monomer

Condensation Polymer Examples Polyamides: carboxylic acid and an amine Kevlar: bullet-proof vests

Condensation Polymer Examples Nylon: fishing line, hosiery, zippers

Condensation Polymer Examples Nomex: flame-resistant clothing and electrical fixtures Proteins