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Chapter 2. Structure and Functional Groups, Intermolecular Forces and Infrared (IR) Spectroscopy. 2.1-2.2 Hydrocarbons: Representative. Carbon-carbon formed the most strongest bond in organic molecules Hydrocarbon: molecules that contain only H & C. Alkanes.
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Chapter 2 Structure and Functional Groups, Intermolecular Forces and Infrared (IR) Spectroscopy
2.1-2.2 Hydrocarbons: Representative • Carbon-carbon formed the most strongest bond in organic molecules • Hydrocarbon: molecules that contain only H & C
Alkanes • Principle sources are natural gas and petroleum • Saturated hydrocarbons • No double or triple bonds • General formula: CnH2n+2 E.g CH4 C2H6 C3H8
Methane gas • Produces carbon dioxide and hydrogen when burning
Alkenes • Unsaturated hydrocarbons: contain double bonds • General formula: CnH2n • Used widely in the industry • Some occurs as plant hormone • Involved in the ripening process
Alkenes • Structure of ethene
Alkynes • Unsaturated hydrocarbon with at least one triple bond • General formula: CnH2n-2 • Use for biosynthesis
Alkynes • Ethyne
Benzene • Six membered ring with alternating single bonds
Polar and NonPolar Molecules • Diatomic molecules with different polarity is a polar molecules • Vectors cancelled out non polar • Dipole moment = charge (in esu) x distance (cm) • Must know 3-D structure
Examples • Using a three dimensional formula, show the direction of the dipole moment of CH3OH. Write ∂- and ∂+ signs next to the appropriate atoms
Functional Groups • Part of a molecule where most of its chemical reaction occur • Defined by characteristic arrangements of atoms • Determined the compound’s chemical properties
Functional groups • Alkyl groups are designated as R • General formula : R-H
Phenyl and Benzyl groups • When benzene group is attached to some other groups of atoms in molecule, it is called phenyl • Abbreviated as Ar
Phenyl and Benzyl groups • The combination of a phenyl group and methylene group ( -CH2-) is called benzyl group
2.6 Alkyl Halides or haloalkanes • Alkyl halides are compounds in which a halogen atom is replaced with a hydrogen atom from alkane • Also known as haloalkanes • General formula: R-X • X = fluorine, chlorine, bromine and iodine • CH3Cl - chloromethane
Alkyl Halides • Classified as being • Primary (1o) • Secondary (2o) • Tertiary (3o)
Examples • Write bond-line structure for • a. An alkane with formula C5H12 that has no secondary or tertiary carbon atoms • b. A secondary alkyl bromide with formula C4H9Br • c. Two constitutionally isomeric primary alky bromide
Alcohols • Hydrocarbons that contain hydroxyl group (OH) • Attached to an sp3-hybridized carbon
Alcohols • Classified as • Primary (1o) • Secondary (2o) • Tertiary (3o)
Examples • Write bond-line structure formulas for • a. Two primary alcohols • b. A secondary alcohols All having the molecular formula C4H10O