Chapter 2
description
Transcript of Chapter 2
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Structure and Functional Groups, Intermolecular Forces and Infrared (IR)
Spectroscopy
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2.1-2.2 Hydrocarbons: RepresentativeCarbon-carbon formed the most strongest
bond in organic moleculesHydrocarbon: molecules that contain only H
& C
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AlkanesPrinciple sources are natural gas and
petroleumSaturated hydrocarbons
No double or triple bondsGeneral formula: CnH2n+2
E.g CH4
C2H6
C3H8
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Methane gasProduces carbon dioxide and hydrogen when
burning
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Methane
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AlkenesUnsaturated hydrocarbons: contain double
bonds
General formula: CnH2n
Used widely in the industry
Some occurs as plant hormoneInvolved in the ripening process
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AlkenesStructure of ethene
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AlkynesUnsaturated hydrocarbon with at least one
triple bondGeneral formula: CnH2n-2Use for biosynthesis
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AlkynesEthyne
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BenzeneSix membered ring with alternating single
bonds
resonance structure of benzene
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Polar and NonPolar MoleculesDiatomic 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
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Cl
C
ClCl
Cl
vector sum = 0no net dipole momentnon polar molecule
Cl
C
HH
H
vector sum = 0 polar molecule
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O
H H
Net Dipole momentPolar molecule
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ExamplesUsing a three dimensional formula, show the
direction of the dipole moment of CH3OH. Write ∂- and ∂+ signs next to the appropriate atoms
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Functional GroupsPart of a molecule where most of its chemical
reaction occur
Defined by characteristic arrangements of atoms
Determined the compound’s chemical properties
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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
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Functional groupsAlkyl groups are designated as RGeneral formula : R-H
CH3CHCH3
isopropyl
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Phenyl and Benzyl groupsWhen benzene group is attached to some
other groups of atoms in molecule, it is called phenyl
Abbreviated as Ar
Ar
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Phenyl and Benzyl groupsThe combination of a phenyl group and
methylene group ( -CH2-) is called benzyl group
BnH2C
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2.6 Alkyl Halides or haloalkanesAlkyl halides are compounds in which a
halogen atom is replaced with a hydrogen atom from alkaneAlso known as haloalkanesGeneral formula: R-X
X = fluorine, chlorine, bromine and iodine
CH3Cl - chloromethane
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Alkyl HalidesClassified as being
Primary (1o)Secondary (2o)Tertiary (3o)
R
H
H
X
1o alkyl halide
R
R
H
X
R
R
R
X
2o alkyl halide 2o alkyl halide
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ExamplesWrite 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
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AlcoholsHydrocarbons that contain hydroxyl group
(OH)Attached to an sp3-hybridized carbon
O H
Functional group of an alcohol
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AlcoholsClassified as
Primary (1o)Secondary (2o)Tertiary (3o)
R
H
H
OH
1o alcohol
R
R
H
OH
R
R
R
OH
2o alcoholor iso_
2o alcoholor tert_
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ExamplesWrite bond-line structure formulas for
a. Two primary alcoholsb. A secondary alcoholsAll having the molecular formula C4H10O