Download Chapter 2_part 1

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
C 2 H6
C 3 H8
Methane gas
 Produces carbon dioxide and hydrogen when
burning
Methane
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
Examples
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
2.5 Alkyl and the symbol R
#C
N1ame
Alkyl (one H has removed)
1
Methane
Methyl
2
Ethane
Ethyl
3
Propane
Propyl
4
Butane
Butyl
5
Pentane
Pentyl
6
Hexane
Hexyl
7
Heptane
Heptyl
8
Octane
Octyl
9
Nonane
Nonyl
10
Decane
Decyl
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