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Organic Functional Groups (12U Chem Nelson) Def’n – a structural arrangement of atoms that imparts particular characteristics to the molecule (eg solubility, polarity, mp,bp, reactivity, etc) - molecules with similar characteristics (due to this structure) are grouped into an organic family (eg alcohols) How to Recognize them 1) carbon-carbon multiple bonds (alkenes, alkynes) 2) Single bonds between CARBON and a more electronegative atom Eg C O C N C Cl 3) carbon atom double bonded to an oxygen atom C═O (called a “carbonyl” group) Priority List (low to high - for nomenclature naming rules) 1) 2) 3) 4) 5) 6) 7) 8) 9) alkyl, halogen (RX), aromatic, nitro (RNO2) alkyne alkene amino (RNH2) alcohol (ROH) ketone (RCOR1) aldehyde (RCOH) ester (RCOOR1) carboxylic acid (RCOOH) Organic Halides (1.1) 1) found in refrigerants (CFC’s), cookware (Teflon), insecticides (DDT), medical disinfectants (“hexachlorophene”) and electrical transformers (PCB’s) 2) carcinogenic concerns, some toxic, air pollution/ozone hole eg. “TCE” (or trichloroethylene) is used as a dry cleaning solvent. It forms free radicals and is pervasive in our water supply due to its density and polarity. Nomenclature aka Prefix X=F Cl Br I eg fluoro chloro bromo iodo alkyl halides “R-X” (R= alkyl part) CH2 ---CH2 Br Br 1,2-dibromoethane Note – R-NO2 “nitro” How to make alkyl halides (see previous notes & eg) 1) Addition reactions with a halogen (Br2) or hydrogen halide (HCl) and an alkene or alkyne 2) Substitution reactions with a halogen (Br2) or hydrogen halide (HCl) and an alkane or aromatic compound Note - Alkyl halides can undergo “elimination” reactions (reverse addition) to make alkenes (need basic conditions) Eg CH2 – CH – CH3 + (OH)-1 CH2 ═ CH – CH3 + H2O + Br -1 H Br 2-bromopropane propene Nitrogen Containing Functional Groups (Sect. 1.7) Amines – an ammonia molecule (NH3) with 1, 2 or 3 hydrogens replaced by an alkyl branch(es). Eg. “A” H2N—CH3 “B” H —N—CH3 “C” H3C—N—CH3 CH3 1o amine (R-NH2) 2o amine (R-N-R1) CH3 3o amine ( R-N-R1) R11 H Nomenclature – prefix “amino” + longest branch, suffix “amine” - 2o and 3o amines include “N” in prefix to denote branch is on Nitrogen - list alkyl branches alphabetically if different in length - two methods used (IUPAC vs suffix method) Example “A” IUPAC name aminomethane Suffix name methylamine “B” N-methylaminomethane dimethylamine “C” N,N-dimethylaminomethane trimethylamine Practice – draw N-ethylamino-n-propane Properties – organic BASES - unpleasant odours eg. (H2NCH2CH2CH2CH2NH2) 1,4-diaminobutane aka “putrescine” - polar area, usually water soluble - important in proteins (“amino acids”) and DNA (nitrogenous base) - prepared by reaction of ammonia (NH3) with an alkyl halide (R-X) (see eg p 73) Nitrogen Compounds “Amides” R—CO—N—R1 R11 - similar structure to an ESTER with a NITROGEN atom replacing the oxygen in the chain. - linkage is called a peptide bond in proteins - formed by a reversible condensation reaction between an AMINE (1o or 2o) and a CARBOXYLIC ACID Properties - weak bases, low solubility in water (unless small molecule) - amount of “H bonding” determines mp/state etc. - can undergo hydrolysis reaction with acid/base catalyst to reform the amine and carboxylic acid Nomenclature suffix = “amide” O H CH3C—OH + H— N—CH3 H—O + 1 amine H small molecule (aminomethane) (water) o Carboxylic acid (ethanoic acid) H+ Heat O CH3—C— N—CH3 H N-methyl ethanamide suffix #C’s in amine #C’s in carboxylic acid NOTE – amide nomenclature is not required in this course Oxygen Containing Functional Groups (Sect 1.4) Alcohols and ethers are ISOMERS of each other. Ethers (R-O-R1 , oxygen bonded to 2 carbon chains) 1) alkyl groups may be the same C length (ROR) or different (ROR1) 2) less polar than alcohols and more volatile (lower bp) 3) generally unreactive but good solvents (if liquid at Rm Temp) and also used as anaesthetics (“diethyl ether”) 4) prepared by condensation reaction of 2 alcohols Nomenclature – 2 ways used CH3 – O – CH2CH3 IUPAC methoxyethane Or methyl ethyl ether (complexity rule used) Alcohols (R-O-H, “hydroxyl” group) 1) contain the “OH” group that is polar 2) classified as 1o, 2o or 3o based on whether C-OH is attached to H or other carbons 3) can have more than one hydroxyl group (“polyalcohol” eg sugars) 4) may be found in rings (cyclo, aromatic) 5) used as polar solvents eg ethanol (alcohol) or 2-propanol (rubbing alcohol) and also as flavourings 6) prepared by addition of water to alkenes (“hydration”) or reduction of aldehydes, ketones or carboxylic acids) 7) also undergo reactions such as : combustion, dehydration/elimination to form an alkene, condensation (with c. acids ester) as well as oxidation reactions (can make ketones, aldehydes, c. acids) Nomenclature suffix = “ol”, prefix = “hydroxyl” Eg. CH3CH2CH2OH = 1-propanol OH hydroxybenzene or phenyl alcohol (phenol) Carbonyl Functional Groups (O═C , Sect 1.5) Def’n – contains a carbon double bonded to an oxygen atom - may be found on an END carbon (“aldehyde”, RCOH) or in the middle of the parent chain (“ketone”, RCOR1) 1) the carbonyl group is polar so these compounds are used as solvents although they have lower boiling points than alcohols (no H bonding) 2) volatile compounds which makes them good chemical “signals” in nature (“smells”) eg. Pheromones, formaldehyde 3) prepared by the controlled oxidation of alcohols which may be reversed by a controlled reduction reaction (Bio connection) Note - [O] = oxidizing agent needed [R] = reducing agent needed [O] eg. A) 2- propanol propanone [R] o “2 alcohol” ketone B) [O] [O#2] 1-propanol propanal propanoic acid [R] [R] o “1 alcohol” aldehyde carboxylic acid C) 3o alcohols don’t easily oxidize [O] methyl- 2- propanol no reaction Nomenclature O Aldehydes – suffix = “al Eg CH3CH2 - C- H propanal Ketones – suffix = “one” O CH3CH2 – C – CH2CH2CH3 3- hexanone Functional Groups with 2 Oxygens (Sect. 1.6) Carboxylic acids – contain the “carboxyl” group (RCOOH) - weak organic acids (acidic H) found in various foods and drugs OH COOH eg. CH3COOH CH3 – CH – COOH O—C—CH3 O acetic acid (ethanoic acid) lactic acid (2-hydroxypropanoic acid) acetylsalicylic acid (ASA) Nomenclature – suffix is “oic” acid (highest priority) Eg. HOCH2CH2CH2COOH 4-hydroxybutanoic acid Properties – polar molecules, high bp/mp due to H bonds - acidic properties/reactions (eg. Neutralization) - formed by the oxidation of an aldehyde [O] [O*] eg CH3CH2OH CH3COH CH3COOH ethanol “sour tasting wine” = ethanol ethanoic acid alcohol + “air” vinegar Reactions Carboxylic acids undergo CONDENSATION reactions with: a) alcohols esters + water “esterification” b) amines amides + water bio = “peptide bonds” General Reaction H+ eg. R—O—H + H—O—CO—R1 R—O—CO—R1 + H—O—H “ester” Esters – an organic “salt” RCOOR1 (Sect. 1.6) - occur naturally in plants used as scents (perfume) and flavourings - polar region (less than carboxylic acids) - prepared by a reversible condensation reaction (usually an alcohol and c. acid) with removal of a small molecule such as water - reaction usually needs an acid catalyst and is sometimes called “esterfication” - reverse reactions (“hydrolysis”) need a strong base (NaOH) eg. saponification (soap making) of a triglyceride or “fat” (Lab 2) - Nomenclature - “alcohol” + “c. acid” suffix = “oate” O CH3CH2CH2C—OH + H—O—CH2CH3 Carboxylic acid Alcohol Butanoic acid Ethanol H+ Heat H— O + H Small molecule O CH3CH2CH2C — O—CH2CH3 from acid from alcohol ester link/bond Name = ethyl butanoate ester suffix #C’s in carboxylic acid #C’s in alcohol Practice – write an esterification reaction for methanol and 2- methylpropanoic acid. Name the ester formed. (water)