Chapter 2_part 1
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Transcript 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