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Hybridization of atoms s all H atoms (shape is always linear) sp any C with only 2 atoms attached (single and triple bond, two double bonds) (shape is linear) sp 2 any C with only 3 atoms attached (double bond) any N or O with a double bond (shape is trigonal planar or bent - 120 °)
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Hybridization of atoms s all H atoms (shape is always linear) sp any C with only 2 atoms attached (single and triple bond, two double bonds) (shape is linear) sp2 any C with only 3 atoms attached (double bond) any N or O with a double bond (shape is trigonal planar or bent - 120°) sp3 Any atom with all single bonds and a complete octet (tetrahedral, trigonal pyramid, or bent – 109.5 °)
Examples – Identify the hybridization, shape, and angles around each atom 1. 2.
Drawing Isomers • Determine the number of unsaturations (ring closures or Π-bonds): • CnH2n+2 = saturated • CnH2n = 1 unsaturation • CnH2n-2 = 2 unsaturations • For every 2 H lost, there is another unsaturation • O does not count • F, Cl, Br, or I counts like an H • Every C has 4 bonds, N has 3, O has 2, H and X have 1.
Examples – Draw molecules (as many as possible) with the following formulas: 1. C8H12 2. C4H6O
Physical Properties of Organic Compounds • Homologous series – melting points and boiling points increase with molecular size • CH4 < C2H6 < C3H8 < C4H10 … • Melting Points and boiling points – depend on intermolecular forces: • Alkanes, alkenes and alkynes – nonpolar (LDF) • Ethers and Halogenoalkanes – nearly nonpolar (LDF, slight dipole-dipole) • Amides, tertiary amines, esters, aldehydes and ketones are polar (LDF and dipole-dipole) • Alcohols, carboxylic acids, primary and secondary amines have LDF, dipole-dipole, and H-bonds. HIGHEST MP AND BP,
Water solubility – depends on intermolecular forces: • More polar (especially if H-bonds), more soluble. • Larger molecule (usually has a larger nonpolar part) becomes less soluble. • Example – CH3OH > C2H5OH > C5H11OH … • Soap – molecules with polar heads and nonpolar tails (allow nonpolar “dirt” to mix with water in micelles )
Solubility and Acid-Base Properties of Organic Substances • Compounds with only C-C or C-H bonds are nonpolar and are soluble in nonpolar solvents and not very soluble in water. • Water soluble organic molecules have polar functional groups. • Surfactants have long nonpolar portions of the molecule with a small ionic or polar tip. • The most important organic acids are carboxylic acids with the • -COOH functional group. • Basic organic molecules are usually amines, -NH2, -NHR, or -NR2 functional groups.
Chirality in Organic Chemistry • A molecule that exists as a pair of nonsuperimposable mirror images is called chiral. The two molecules are called stereoisomers or enantiomers. • Organic compounds that contain one carbon atom that is attached to four different atoms or groups are chiral. • Stereoisomers have the same structural formula but different arrangements of atoms in space.
Chirality in Organic Chemistry • Consider *CHBr(CH3)(CH2CH2CH3). The *C is attached to: (i) H, (ii) Br, (iii) CH3, and (iv) CH2CH2CH3:
Chirality in Organic Chemistry • Chiral molecules exist as a pair of enantiomers. • The enantiomers are nonsuperimposable mirror images. • Organic chemists label enantiomers as R and S. • If two enantiomers are placed in a solution in equal amounts, then the mixture is called racemic. • If one molecule contains two stereogenic centers, one R and one S, then the molecule shows no optical activity. • Many pharmaceuticals are chiral molecules.
Condensation Polymerization (ex – nylon, polyester) • Produces H2O + H2O