Organic Chemistry

1
Organic Chemistry

• Introduction
• Alkanes

Mr. Shields Regents Chemistry U16 L01
2
Organic Chemistry

• Organic Chemistry involves the study of Carbon
  based compounds of which there are millions and
  many more yet to be made
• Much more diversity than found in inorganic
  compounds
• What are some examples of Carbon Based compounds?
• Petrochemicals - Biochemicals
• Dyes - Polymers
• Pharmaceuticals - Life

3
Source

• The source of almost all organic compounds today
  is petroleum
• Crude oil
• Through Synthesis hydrocarbons can be further
  modified into other organic compounds
• Petroleum (crude oil) is first separted into
  several different categories at refineries
• Separation at refineries is a distillation
  process based on BP (mol. Wt.)

4
Why so many C compounds?

• Carbon atoms can bond with other carbon atoms in
  chains. These bonds are Covalent.
• Since Carbon has 4 unpaired electrons it can form
  4 covalent bonds.

C
5
Formation of Carbons 4 covalent bonds
Carbons ability to form 4 covalent bonds, even
with itself, leads to carbons ability to form
millions of different compounds, some simple
some very complex.
6
Properties of Covalent Substances

• Covalent compounds are Molecular Compounds
• What do we mean by Molecular and What kind of
  properties do they have?
• Low melting points boiling points
• Poor conductors of heat electricity
• Solids tend to be soft
• Can not be worked (not malleable)
• May be Polar or nonpolar
• Non-polar is not soluable in water
• Polar may be slightly sol. to sol. in water
• Non-polar will dissolve in non-polar solvents
• React more slowly than ionic compounds

7
Structural Formulas

• Shows kind number of atoms and how they are
  bonded together.
• They are 2-D drawings of 3-D objects so
  structural formulas arent totally realistic.
• H
• HCH
• H

8
Structural Formulas

• A single line represents one pair of
• electrons (a single bond).
• A double line represents two pairs of
• electrons (a double bond).
• ? A triple line represents three pairs of
• electrons (a triple bond).

9
Condensed Structural Formulas

• These formulas show kind number of atoms as
  well as some information regarding what atoms are
  joined to what atoms but not how.
• They dont depict bonds
• Examples CH4, CH3OH, CH3Cl, CH2Cl2,
• CH3CH2CH2CH3, CH3COOH

10
Molecular Formulas

• These formulas show kind number of atoms but
  not necessarily any other information
• Condensed Structural formula
• Examples CH3OH, CH3CH2CH2CH3, CH3COOH
• Molecular formula
• Becomes CH4O, C4H10,
  C2H4O2

11
Molecular Shape

• When carbon is bonded to 4 other atoms carbon is
  at the center of a tetrahedron and the 4 other
  atoms are located at the corners.
• This is known
• As a
• Tetrahedron
• If there are 3 Cs
• Bonded to each other
• Then there are 3 joined
• tetrahedrons

12
Vocabulary Interlude

• Hydrocarbons organic compounds containing only
  Carbon and Hydrogen.
• Straight chain All internal C bonded to only 2
  other Cs
• Ex c-c-c-c-c-c-c
• Branched One or more int. C bonded to 3 or 4
  other Cs
• Ex

c-c-c-c-c-c-c-c c
c c c-c-c
c
13
Vocabulary

• Saturated organic compounds containing only
  single bonds (carbon bonded to 4 atoms)
• Unsaturated organic compounds containing one or
  more double or triple bonds.

14
Vocabulary

• Homologous Series a group of compounds with
  related structures and properties.
• Each member of the series differs from the one
  before it by the same additional unit. (Ex. The
  Alkanes each differs by one -CH2 unit)

Ex CH4 C2H6 C3H8
15
Primary Categories of Hydrocarbons

• There are 3 major Hydrocarbon Categories
• These can be Straight Chain or Branched
• Alkanes (Single Bonds) hydrogen 2n 2
• CH3CH2CH2CH3
• Alkenes (Double Bond) H 2n
• CH3CH2CHCH2
• Alkynes (Triple Bond) H 2n 2
• CH3CH2C CH

Table Q in your Reference Tables is where you
can Get this information!
16
Naming straight-chain Alkanes

• All alkane names have the suffix ane.
• The prefix depends on the number of Cs.

Ex Methane 1 Carbon Ethane 2 Carbon Whats
the Molecular formula of each?
17
Prefix of C atoms
Meth ane 1
Eth 2
Prop 3
But 4
Pent 5
Hex 6
Hept 7
Oct 8
Non 9
Dec 10
(Check out Table P in your Reference Tables)
18
Alkanes
Formula Name
CH4 Methane
C2H6 Ethane
C3H8 Propane
C4H10 Butane
C5H12 Pentane
C6H14 Hexane
C7H16 Heptane

• A Homologous series of saturated hydrocarbons.
• Compounds with a related structure differing by
  the same repeating unit (-CH2-)
• General formula is CnH2n2 (n no. of carbon
  atoms)

Problem Whats the molecular formula for
the alkane with 27 carbon
19
Problem What is the structural formula for
pentane?
(Shown w/o the Hydrogens)
C-C-C-C-C
Problem What is the name of the following
Hydrocarbon?
Hexane!
Is it a branched or straight chain hydrocarbon?
20
Properties of Alkanes

• Physical Properties Change systematically with
  the number of Cs
• As the number of Cs
• In a homologous
• series increases, the b.p. m.p. increases.

Mol. Formula M.P. B.P.
CH4 -182 -162
C2H6 -183 -89
C3H8 -188 -42
C4H10 -138 -0.5
C5H12 -130 36
C6H14 -95 69
C7H16 -91 98
C8H18 -57 126
C9H20 -54 151
(Due to increasing Intermolecular force in the
form of temporary dipoles)
21
SIMPLE HYDROCARBONS

• Draw the structural formula, condensed structural
  formula and molecular formula for the following
• propane
• Octane
• Which should have the highest M.P B.P.?