SCHWAN LECTURE 25€¦ · Web viewmany isomers available and their number increases with increasing...
Transcript of SCHWAN LECTURE 25€¦ · Web viewmany isomers available and their number increases with increasing...
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L28-1
SCHWAN LECTURE 28CHEM*1040
Last meeting: Lecture 27
· Complete Bond types
· Intermolecular forces
· Introduction to Organic Chemistry
Today:Þ Continue Introduction to Organic Chemistry
Þ concept of functional groups
Þ Hydrocarbons
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Organic compounds prevail in:
foods: carbohydrates, fats, food flavorings,
preservatives, proteins, vitamins, colorings
fuel: wood, coal, heating oil, natural gas.
clothing: natural fibers (cotton, wool, silk),
modified natural fibers (rayon), synthetic fibers
(nylon, polyesters, acrylics), dyes.
transportation: gasoline, lubricating oils,
rubber and elastomers, plastics, insulation.
health: antibiotics, antihistamines, pain killers,
antimalarials, anticancer drugs, other drugs.
other: soaps and detergents, cosmetics,
explosives, pesticides, herbicides, paints, paper,
pigments.
Plastics, in your body
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Family Functional Group
Example
alkanes none CHH
CH
HH
H
ethane
alkenes C C C CH
H
H
H
ethene or ethylene
alkynes C C C CH H ethyne or acetylene
alkyl halides
C X CClCl
ClCl carbon
tetrachloride
ethers C O CCH2OCH2
CH3 CH3ethyl ether
alcohols C OH CHH
HOH methanol
aldehydes CO
H CHH
HCO
Hethanal or
acetaldehyde
ketones CO
CO
CH
HH
CH
HH
propanone or acetone
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amines N CHH
HNH2 methylamine
carboxylic acids C
OOH CC
OOHH
H
H
acetic acid
esters CO
O CCO
HH
HO C
HH
Hmethyl acetate
amides CO
N CCH3
ON HH
acetamide
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Alkanes
The alkanes are described by the group
formula CnH2n+2, where n = 1,2,3,... .
hence the list includes CH4, C2H6, C3H8, and so on.
Successive members differ by
one CH2 (methylene) group.
All carbons are tetrahedral in nature:
(condensed)
CH
H HH
109.5° H CH
HH
CH4
(three-dimensional) (projection)
or
- may be to H’s or other carbons
said to be “saturated”
implies having only carbon-carbon single bonds,
therefore the maximum number of hydrogen atoms per carbon atom,
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Molecular Formulas, IUPAC Names, and Structural Formulas of First Ten Alkanes
formula name structure
CH4 methane CH4
C2H6 ethane CH3CH3
C3H8 propane CH3CH2CH3
C4H10 butane CH3CH2CH2CH3
C5H12 pentane CH3(CH2)3CH3
C6H14 hexane CH3(CH2)4CH3
C7H16 heptane CH3(CH2)5CH3
C8H18 octane CH3(CH2)6CH3
C9H20 nonane CH3(CH2)7CH3
C10H22 decane CH3(CH2)8CH3
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isomers of pentane: label 1°, 2°°andº
CH3CH2CH2CH2CH3
CH3CH2CHCH3
CH3
CH3CCH3
CH3
CH3
many isomers available and their number increases with
increasing carbons
molecules may also be drawn
H3C CH3
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Nomenclature: (p. 10)
as a prefix, alk - ane becomes alk - yl
Rules
1. Identify and name the longest continuous
chain of carbon atoms.
2. Precede with name and number (by position)
of substituents, and start number system as
early as possible
3. Use prefixes when more than one of the same
substituent are present: di, tri, tetra, penta, hexa,
4. list substituents alphabetically ignoring
prefixes
5. Punctuation: words not separated; separate word and
number by hyphen separate numbers by comma
Some examples:
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CH3 CH
CHCH3
CH2CH3CH3
CH3
2,3-dimethylhexane
CH3CH2CH2CHCHCH2CHCH3
CH3
CHCH3
CH3CH2
4,5-diethyl-2-methyloctane
Common Alkyl Substituents
methyl
ethyl
propyl
isopropyl
t-butyl
CH3
CH3CH2
CH3CH2CH2
CH3CHCH3
CH3 CCH3
CH3
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Cycloalkanes -saturated hydrocarbons with
general formula C2H2n
alkane, C2H2n+2 cycloalkane, C2H2n
CH2H2CH2C
C CCH2
HHH
H HH
CH2H2CH2C
C CCH2
HHH
H
orC
CC
C
H
H
H
H H
H
H
HH
HH
HH
CCCC
H HH
orcyclobutane
or
H
H HH C
C
C
H
HH
H
H
HC
CCH2
CH2
CH2 CH2
CH2 orcyclopentane
orCH
H
H
H CC
H
HC C
CHH
H
H
H
Horcyclopropane
oror
H
H
H
H
H C
CC
C
CC
H
H
H
HH
H
H
CH2
CH2CH2
CH2CH2
CH2
cyclohexane
60°
90°
108°
109.5°with flex as shown
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L28-11CH2CH3
CH3
name: 1-ethyl-2-methylcyclohexane
see Toolbox p. JA 481 for naming hydrocarbons
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Alkenes and Alkynes fewer than the maximum number of
hydrogen atoms
alkenes -double bond C=C
alkynes -triple bond, CºC
Because of the presence of the multiple bond
these are unsaturated hydrocarbons
characteristics of alkenes
possess double bond, general formula: CnH2n
telltale suffix in nomenclature: ‘ene’
two p-orbitals perpendicularto the plane of the molecule
CH C HHH oneC C HH
HH_ bondC2p C2p
overlap
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characteristics of alkynes
possess triple bond, general formula: CnH2n-2
telltale suffix in nomenclature: ‘yne’
180° 180°
C CH H or CH CH geometry: C CH H;
C CH HCsp
_ H1s (one of two)bond
Csp C_sp bond
bond skeleton
C CH H two bonds
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geometric isomerism may be present in alkenes
and we employ the cis and trans terminology
C CHH
CH3CH2 CH2CH3
C CCH2CH3H
CH3CH2 H
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IUPAC Nomenclature of Alkenes & Alkynes
Follow nomenclature for alkanes but remember to
a) indicate the position of the multiple bond with a number
b) make sure the multiple bond is part of the backbone
But , for alkene, use suffix ‘ene’.
But , for alkyne, use suffix ‘yne’.
Some examples
CH3CHCH2CH2CHC CH
CH2CH3
CH3
3,6-dimethyl-1-octyne
Benzene and Aromatic Hydrocarbons
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During the early 1800’s a group of naturally-
occurring compounds, One particular one was
found to have a molecular formula of C6H6. In
1880, its structure was found to be
CC
CCC
CHH
H
HHH
orCC
CCC
CHH
H
HHH
bond length between C-C single () bond and a
C=C double ( + ) bond
some examples
H120° 120°
120°
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OH CH3 NH2O OH
Nomenclature of Benzene Derivatives
ortho meta para
Another note: A benzene ring
can also be treated as a
substituent. Call the C6H5-unit
“phenyl”.