Introduction to Organic Chemistry

1
Introduction to Organic Chemistry

• Organic Chemistry The chemistry of carbon
  compounds
• Carbon contains four valence electrons and as a
  result normally forms four bonds in neutral
  organic compounds.

2
Electronegativity

• Tendency or ability of an atom to attract bonding
  electrons

Electronegativity increases
Electronegativity increases
3

• Metal elements have low electronegativity values
• Non-metal elements have high electronegativity
  values

Electronegativity increases
Electronegativity increases
4
Polarity and Polar Bonds
Non-polar bonds

• The atoms in a nonpolar covalent bond have
  electronegativity differences of 0.4 or less.
• Examples
• Atoms Electronegativity Difference
  Type of Bond
• N-N 3.0 - 3.0 0.0 Nonpolar
  covalent
• C-P 2.5 - 2.1 0.4 Nonpolar
  covalent
• H-C 2.1 2.5 0.4 Nonpolar
  covalent

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Polar Bonds

• The atoms in a polar covalent bond have
  electronegativity differences of 0.5 to 1.6.
• Examples
• Atoms Electronegativity Difference
  Type of Bond
• O-H 3.5 2.1 1.4 Polar covalent
• N-C 3.0 - 2.5 0.5 Polar covalent
• O-S 3.5 - 2.5 1.0 Polar covalent

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Alkanes

• Contain only C and H (hydrocarbons)
• Have only single C - C bonds.
• Have the general formula of CnH2n 2
• C atoms H atoms formula
• 1 2(1) 2 4 CH4
• 3 2(3) 2 8 C3H8
• 6 2(6) 2 14 C6H14

7
Structural Formulas

• Structural formulas show the arrangement of
• atoms in an organic compound.
• In expanded structural formulas, all the
  individual bonds are drawn.
• In condensed structural formulas, each carbon is
  written with the H atoms connected to it.

8
Line-Bond Formulas

• A line-bond formula abbreviates the carbon chain
  and shows only the zigzag pattern of bonds from
  carbon atom to carbon atom.

9
IUPAC System of Naming Alkanes

• The IUPAC (International Union of Pure and
  Applied Chemistry) establishes the rules for
  naming organic compounds.
• Alkanes are named with ane endings.
• The first four alkanes are methane, ethane,
  propane, and butane.
• The names of longer carbon chains use Greek
  prefixes (Table 11.2 pg. 419).

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Branched-Chain Alkanes

• In a branched-chain alkane, a side group called a
  branch or a substituent is attached to a carbon
  chain.

11
Alkyl Groups

• An alkyl group
• Is derived from the corresponding alkane by
  removing one hydrogen (Table 11.5 pg. 424).
• Is named by replacing the ane ending of the
  corresponding alkane with yl.
• For example, if it is derived from methane it is
  called a methyl group.

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Naming Branched Alkanes

• In the IUPAC system
• The longest continuous carbon chain is named as
  the main chain.
• Any carbon branches use their alkyl names.
• Each branch is numbered by counting the main
  chain from the end nearest the first side group.
• Branches are listed in alphabetical order.

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Give the IUPAC name for each alkane. A.
CH3 CH3
CH3CHCH2CHCH3 B.
CH2CH3 CH3
CH3CH2CHCH2CCH2C
H3 CH3
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Drawing Structures from IUPAC Names
2,4-dimethylhexane 2, 4
dimethyl hexane Location of
Two CH3- groups 6 carbon main
chain branches on attached with
single C-C bonds main chain
15
Constitutional Isomers

• Molecules that have the same molecular formula
  but different structures (arrangement of atoms).
• Draw the constitutional isomers for C4H10

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Cycloalkanes

• Cycloalkanes
• Are rings of carbons that can be drawn as
  geometric figures.
• Have a general formula of CnH2n or 2 less
  hydrogens than the alkane. propane - C3H8
  cyclopropane C3H6. butane - C4H10
  cyclobutane C4H8.
• Are named with the prefix cyclo- in front of the
  corresponding alkane name.

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Formulas of Some Cycloalkanes

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Alkenes and Aromatic Compounds

• Hydrocarbons that contain one or more
  carbon-carbon double bonds (alkynes contain one
  or more triple bonds).

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Geometric Isomers

• Unlike single bonds, rotation around a double
  bond does not occur.
• Because of the restricted bond rotation, some
  alkenes and aromatic compounds exists as cis
  and/or trans isomers.