Functional Groups A functional group is a small

Functional Groups A functional group is a small group of atoms that lend characteristic properties to the molecule Properties of the molecule are dictated by the functional groups; allows for systematic study of organic molecules

Halides: R-X where R is any alkyl group, and X a halogen CH 3 Cl - chloromethane C 6 H 5 Cl - chlorobenzene Synthesis: radical chain reaction between an alkane and a halogen CH 4 + Cl 2 hn or heat CH 3 Cl + HCl 2 Cl • • Cl + CH 4 HCl + • CH 3 + Cl 2 CH 3 Cl + • Cl

Alcohols: R-OH hydroxyl functional group Nomenclature - use the suffix “ol” CH 3 -CH 2 -OH ethanol CH 3 -CH 2 OH 1 -propanol Primary alcohol Secondary alcohol Tertiary alcohol

Presence of OH group allows hydrogen bonding As the C chain becomes longer the OH group becomes less important Charge distribution in ethanol; red indicates negative charge Synthesis of alcohols Hydrolysis of a alkyl halide with a strong base OH- + CH 3 Br CH 3 OH + Br. Addition across a double bond CH 2=CH 2 + H 2 O 300 - 400 o. C 60 - 70 atm CH 3 CH 2 OH

Phenols: hydroxyl group attached directly to an aromatic ring Phenol (C 6 H 5 OH) weak acid, Ka = 1 x 10 -10; stability of the phenolate ion (C 6 H 5 O-)

Oil of thyme Oil of clove

Ethers: R - O - R C 2 H 5 - O - C 2 H 5 C 6 H 5 - O - C 2 H 5 Synthesis: H SO 2 R-OH 2 4 diethylether ethylphenylether R - O - R + H 2 O Kinetics vs thermodynamics CH 3 -CH 2 -OH + CH 3 -CH 2 -OH H 2 SO 4 140 o. C 180 o. C 2 CH 2=CH 2 + 2 H 2 O CH 3 -CH 2 -O-CH 2 -CH 3 + H 2 O

Aldehydes and Ketones carbonyl group aldehyde ketone HCHO: formaldehyde CH 3 CHO: acetaldehyde CH 3 COCH 3: dimethlyketone (acetone)

Properties of aldehydes and ketones differ because of the aldehyde H atom CH 3 CH 2 OH 1 o alcohol ethanol (CH 3)2 CHOH 2 o alcohol 2 -propanol O 2, catalyst, CH 3 CHO aldehyde acetaldehyde high temperatures O 2, catalyst, high temperatures (CH 3)2 CO dimethylketone

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Carboxylic acids: -COOH functional group HCOOH - formic acid (ant venom) CH 3 COOH - acetic acid (vinegar) Carboxylic acids hydrogen bond - “dimers” Synthesis Catalytic oxidation of aldehydes CH 3 CHO O 2, Mn 2+ CH 3 COOH

Esters: R-COO- R’ acetic acid + ethanol ethylacetate

Fats (solids) and oils (liquids) are triesters formed from glycerol and three carboxylic acids (fatty acids) Tristearin: animal fatty acid tri-esters CH 2 OHCH 2 OH + 3 CH 3(CH 2)16 COOH glycerol stearic acid Saturated - C-C single bonds Unsaturated - one (mono-unsaturated) or more (polyunsaturated) C=C bonds

Amines: ammonia primary amine (1 o) secondary amine (2 o) tertiary amine (3 o)

CH 3 NH 2 (CH 3)2 NH (CH 3)3 N C 6 H 5 NH 2 methylamine dimethylamine trimethylamine aniline Amines are bases: Nic. H 2+(aq) + 2 NH 3(aq) Nic(aq) + 2 NH 4+(aq) Synthesis of amines a) Naturally occurring b) NH 3 + CH 3 Cl CH 3 NH 2 + HCl nicotine

Amino acids: carboxylic acid containing an amine group Glycine: NH 2 COOH

cationic form predominant in acidic solutions dipolar form zwitterion anionic form predominant in basic solutions

Amides: -CONH 2 - group Formed by reaction between NH 3 or 1 o or 2 o amine and acid

glycine + glycine diglycine + H 2 O Proteins: polypeptides with CONH linkage between amino acids http: //www. cryst. bbk. ac. uk/pps 97/course/section 3/helix. pdb