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Zumdahl

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That they were a product of life's vitality. ... Old Possum's Naming. After n=4, the prefixanes have Greek numbers as their prefixes. ... – PowerPoint PPT presentation

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Title: Zumdahl


1
Zumdahls Chap. 22
  • Organic Chemistry

2
Chapter Contents
  • Introduction
  • Alkanes CnH2n2
  • Isomers
  • Nomenclature
  • Cycloalkanes CnH2n
  • Alkenes CnH2n
  • Alkynes CnH2n2
  • Aromatics
  • Functional Groups
  • Alcohols
  • Aldehydes
  • Ketones
  • Carboxylic Acids
  • Esters
  • Amines

3
Organic Chemistry
  • Once upon a time
  • It was believed that organic chemicals could only
    arise in life processes
  • That they were a product of lifes vitality.
  • In 1828, German chemist Friedrich Wöhler
    dispelled that myth when
  • (Mineral) ammonium cyanate, NH4CNO, heated gave
    (organic) urea, (NH2)CO(NH2). As if we needed
    another source.

4
Modern Views
  • With the exception of petroleum products,
    geological and elemental carbon is inorganic
    carbon.
  • Other carbon-containing molecules are organic by
    virtue of carbons presence.
  • There are no end to the combinatorial
    possibilities since C bonds to C!

5
Carbons Flexibility
  • sp, sp2, sp3 mean a rich geometry of 180, 120,
    and 109.43 angles in virtually endless chains
    and branches of organic molecules.

The most potent psychotropic chemical cocktail on
Earth
CHOCOLATE!
6
Carbons Reactivity
  • NOT.
  • With the exception of unsaturated sites (multiple
    carbon-carbon bonds), it is at the heteroatoms
    (non-CH atoms, X) in an organic molecule where
    lies the reactive site.
  • Common CX combinations are called functional
    groups and dictate reactivity.

7
Inorganic Carbon
  • Elemental carbon
  • Graphite
  • Diamond
  • Buckminsterfullerene
  • Carbon oxides and halides
  • Carbonates and carbides
  • Simple cyano- compounds like HCN.

8
ALKANES
  • Saturated hydrocarbons, CnH2n2.
  • Saturated because they cant take any more
    hydrogen atoms!
  • Straight chains are H3C(CH2)n2CH3
  • Gaseous for nlt5 solid for ngt17 _at_ STP.
  • Inert (but for strong oxidizers)
  • Pathologically nonpolar.
  • Waxes, oils, fuel gases as n decreases.

9
Old Possums Naming
  • After n4, the prefixanes have Greek numbers as
    their prefixes.
  • 5pent, 6hex, 7hept, 8oct, 9non, and 10dec,
    20eicos, 30triacos
  • But n?4 are named historically
  • CH4, Methane (intoxicate from the Greek)
  • Ethane, Propane, and Butane for 2,3,4.

10
Branching Isomers
  • After n3, its possible to let some Cs bond
    with more than 2 other carbons.
  • But fewer than 5, of course!
  • The of structural isomers possible thereby
    grows exponentially with n.
  • These isomers have similar chemical and physical
    properties.
  • So theyre a bit expensive to separate, and one
    sees bottles labeled merely hexanes.

11
Isomer Naming
  • Older conventions would have that as isooctane,
    but a good IUPAC name results from the following
  • Name the longest C chain (pentane)
  • List the side groups in alphabetical order with
    Greek prefixes (trimethylpentane)
  • Supply (smallest possible) positional indices
    (2,2,4 trimethylpentane)
  • The gasoline power rating standard molecule.

12
Cycloalkanes, CnH2n
  • If the two end Cs lose 1 H each, they have free
    valence to close a ring voila,
    cyclo(whatever)ane.
  • Again properties similar to straight chains.
  • Can now have conformational isomers!
  • E.g., BOAT cyclohexane versus CHAIR

13
Alkenes, CnH2n
  • Cycle formation isnt the only possible result of
    dehydrogenation.
  • Adjacent Cs can double bond, CC, making an
    (unsaturated) alkene.
  • Much more reactive (vulnerable ? e pair)
  • Rigid ? orbitals ? rigid planar partners!
  • E.g., trans-5-methyl-2-hexene

14
Alkene Isomers
  • While an sp3 CX2Y2 has only 1 isomer,
  • (every X and Y is adjacent to all the others)
  • the sp2 alkene C2X2Y2 has cis trans isomers
    (where X is or isnt on the same side of as X).
  • For longer hydrocarbons, cis trans refer to the
    side the chain extends

15
Alkynes, CnH2n2
  • sp triple bonding makes a rigid 180 segment in a
    hydrocarbon.
  • It too is vulnerable to attack across the
    multiple bond site.
  • Double triple bonds can suffer addition where
    an AB molecule single bonds A and B to an
    unsaturated site. H2, HX, and X2 (where X is
    halogen) are favorites.

16
Unsaturated Cycles
  • Earlier we noted the stability lent to benzene,
    C6H6, by ? MOs.
  • Alternating single/double cycles occur in many
    organic molecules similarly.
  • This class is called aromatic (by virtue of
    their aroma).
  • The ? structure is often preserved in their
    chemical reactions they dont add, they
    substitute instead.

17
Functional Groups
  • Organic backbones can bear hetero-atoms as
    reactive sites.
  • Alkyl root symbolized as R, a generic hydrocarbon
    radical (methyl, ethyl, etc.)
  • Functional groups append R, e.g.,
  • ROH, an alcohol, or RCHO, aldehyde.
  • RCO2H, a carboxylic acid, RNH2, amine.

18
Alcohols, ROH
  • The OH makes alcohol polar enough to hydrogen
    bond. ? water soluble
  • Fermentation product but vulnerable to oxidation
    to aldehyde and acid.

19
Aldehydes, RCHO
  • Next C oxidation state up from alcohol.
  • Degradation product in your liver!
  • If CO isnt a chain end substituent, its not an
    aldehyde but a ketone.
  • Aldehydes are often flavorings, but
  • Ketones are industrial solvents.

20
Carboxylic Acids RCO2H
  • Usual highest C ox. state in organics.
  • End product of bodys alcohol degradation.
  • Weakly acidic but important buffers.
  • React with alcohols to make highly flavorful
    esters a condensation rxn.


?

21
Amines, RnNH3n
  • Come in three varieties, n 1, 2, 3.
  • Primary amines, n1, are at chain end.
  • Secondary amine N bonds to 2 carbons.
  • Tertiary amines bond to 3 C.
  • Weak base Kb diminishes as n increases.
  • Alcohols are also primary, secondary, and
    tertiary. (Primary are on end carbons.)
  • But this refers to the bonding of the C to which
    OH is attached.

22
Mixed Functionality
  • So H2NCH2CH2OH is an alcohol and an amine it
    becomes ethanolamine.
  • But the monster C9H14N4O3 would be agony to call
    by its IUPAC name.
  • So its known by it common name, carnosine.

How many Ka and Kb are expected?
1 and 4, respectively.
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