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- Historically - compounds from living systems (plants and animals)
- A “vital force”, ie. life was thought to be necessary to make organic
chemicals.
- In 1828 Wohler synthesized urea from purely inorganic chemicals.
- Urea, found in urine, was definitely an organic compound!
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- The Study of Carbon Compounds
- (some exceptions: for example carbonates, carbon dioxide, etc.)
- Biochemistry is now the field that studies chemicals of life.
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- Foods
- Carbohydrates
- Fats
- Proteins
- Clothing
- silk, linen, wool,
- cotton, Dacron,
- Nylon, Orlon,
- etc.
- Plastics
- Pharmaceuticals
- Detergents and Soaps
- Pesticides
- Gasoline and oils
- Water purification
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- 1. Forms four covalent bonds
- 2. Bonds covalently to: H, O, N, P, S, and all other nonmetals (except noble gases)
- 3. Carbon atoms join to form:
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- 4. Carbon can form multiple bonds to itself, oxygen, and nitrogen.
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- 4. Many carbon compounds exist in the form of isomers.
- Isomers are compounds with the same molecular formula but different
structures.
- An isomer example: A, B, and C all are C4H10 but
have different structures. See
the next slide!
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- Isomer Examples. All C4H8
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- Hydrocarbons contain only carbon and hydrogen.
- They are nonpolar molecules and consequently are not soluble in water
but are soluble in typical nonpolar organic solvents like toluene or
pentane.
- Hydrocarbons are constructed of chains or rings of carbon atoms with
sufficient hydrogens to fulfill carbons need for four bonds.
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- Aliphatics Aromatics
- Structures Based On:
- Chains and Benzene
ring
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- Aliphatics Aromatics
- Alkanes and cycloalkanes
- Alkenes and cycloalkenes
- Alkynes and cycloalkynes
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- Alkanes are compounds that contain only carbon-carbon and
carbon-hydrogen single bonds.
- For example:
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- alkenes have a carbon-carbon double bond
- alkynes have a carbon-carbon triple bond
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- alcohols have the general formula:
- ROH (R is a carbon group)
- ethers have the general formulas:
- R-O-R, Ar-O-R, Ar-O-Ar
- Ar is also a carbon group but is “aromatic”
- phenols have the general formula:
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- aldehydes have the general formula
- R1 may be H or any carbon group
- ketones have the general formula
- neither R1 nor R2 can be H
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- carboxylic acids have the general formula
- esters have the general formula
- R1 may be carbon or H but R2 cannot be H or it would be an acid!
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- acid chlorides have the general formula
- anhydrides have the general
formula
- R1 usually is the same as R2 and neither is H
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- amines have one of these general formulas
- R groups may be alkyl or aromatic
- amides have the general formula
- All Rs may be carbon or H
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- thiols (mercaptans) have the general formula
- disulfides have the general formula
- R is any carbon group
- Rs may be different
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- 1 an amine
- 2 a carboxylic acid
- 3 an ester
- 4 an alkene
- 5 an aldehyde
- 6 an alcohol
- 7 a ketone
- 8 a thiol
- 9 an anhydride
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- The title shows the general formula for a chain alkane.
- The first ten alkanes are:
- methane CH4 hexane C6H12
- ethane C2H6 heptane C7H16
- propane C3H8 octane C8H18
- butane C4H10 nonane C9H20
- pentane C5H12 decane C10 H22
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- The Lewis dot and condensed formulas for methane.
- The Lewis dot and condensed formulas for ethane .
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- Lewis dot vs condensed formulas: propane.
- Terminal carbons condense to CH3 with the hydrogens usually
to the right of the carbon.
Interior carbons condense to CH2 .
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- A branch or substituent on a chain may be condensed into the chain
usually after the carbon from which it branches.
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- The IUPAC (International Union of Pure and Applied Chemistry) is responsible for chemistry names.
- Before learning the IUPAC rules for naming alkanes, the names and
structures of eight alkyl groups must be learned.
- These alkyl groups are historical names accepted by the IUPAC and
integrated into modern nomenclature.
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- An alkyl group is an alkane with one hydrogen atom removed. It is named by replacing the ane of
the alkane name with -yl.
- Methane becomes a methyl group.
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- All six hydrogens on ethane are equivalent. Removing one H generates the ethyl
group.
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- Propane: removal of a hydrogen generates two different propyl groups
depending on whether an end or center H is removed.
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- n-butane gives two butyl groups depending on whether an end (1o)
or interior (2o) H is removed.
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- Isobutane gives two butyl groups depending on whether a 10 or
30 H is removed.
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- 1. The base or parent name for an alkane is determined by the longest
chain of carbon atoms in the formula.
Note: the longest chain may bend and twist. It is seldom horizontal!
- Any carbon groups not part of the base chain are called branches or
substituents.
- These carbon groups are also called alkyl groups.
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- Rules 1 applied. Find the longest
chain in each molecule. (Click
for answer.)
- A=7 B=8
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- 2. Number the carbon atoms in the chain starting from the end with the
first branch. If both branches
are equally from the ends, continue until a point of difference occurs.
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- Left: first branch is on carbon 3.
- Right: first branch is on carbon 3 (From top) not carbon 4 (If from
right).
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- 3. Prefix the branches/substituents in alphabetical order before the
base/stem name (longest chain).
Halogens usually come first.
- Indicate the position of the branch on the main chain by prefixing its
name with the carbon number to which it is attached. Separate numbers and letters with a
hyphen.
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- Hyphenated and number prefixes are not considered when alphabetizing
groups.
- Name the compound below.
- 5-sec-butyl-4-isopropylnonane
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- When a branch/substituent occurs more than once, prefix the name with
di, tri, tetra,etc. Then prefix
the number to the name with a separate number for each occurance. Separate numbers with commas.
- eg. 3,4-dimethyl or 4,4,6-triethyl
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- 6-ethyl-6-isobutyl-3,3-dimethyldecane
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- Constitutional/Structural Isomers differ in how atoms are
connected. The two isomers of
butane are shown below. The
carbon atoms are connected in different patterns.
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- Cycloalkanes have two less hydrogens than the corresponding chain
alkane.
- Hexane=C6H14; cyclohexane=C6H12
- To name cycloalkanes, prefix cyclo to the name of the corresponding
alkane.
- Place substituents in alphabetical order before the base name as for
alkanes.
- For multiple substituents, use the lowest possible set of numbers. A single substituent requires no
number.
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- Two groups may be on the same side (cis) of the imagined plane of the
cycloring or they may be on the opposite side (trans). The two isomers are referred to
geometric or cis-trans isomers.
E. g.
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- Conformations differ only in rotation about carbon-carbon single
bonds. Two conformations of
butane are shown below. The first
(staggered form) is more stable because it allows hydrogens to be
farther apart and thus the atoms are less crowded.
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- Chair form Boat form
- (more stable)
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- All alkanes undergo:
- Combustion to carbon dioxide and water
- Halogenation to haloalkanes
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