Alkanes and Their Stereochemistry

1
Chapter 3

• Alkanes and Their Stereochemistry

2
Functional Groups

• Functional groups are a group of atoms that has
  similar characteristic chemical behavior in every
  molecules where it occurs.
• Think of functional groups as individuals in a
  team. They bring their special abilities yet
  they all function as a unit or team.
• There are many functional groups with different
  properties.

3
Carbon Carbon Functional Groups

• When a carbon is bound to a second carbon only 4
  possibilities arise.
• Alkane Carbon Carbon (Single Bond - SP3)
• Alkene Carbon Carbon (Double Bond SP2)
• Alkyne Carbon Carbon (Triple Bond SP)
• Arene Carbon Carbon (Aromatic Ring
  Resonance Structures)
• Properties Covalent Bonds (Oil Soluble)

4
Basic Carbon Structures Carbon
5
Carbon Oxygen (Single Bond)

• When a carbon is singly bound to a oxygen the
  most common functional possibilities are
• Alcohol (C-OH) are used as antiseptic, beverage,
  etc
• Ether (C-O-C) are used as solvents for synthesis.
• Phosphate (C-O-PO3) found in DNA, RNA, and many
  biological molecules.
• Properties Polar Covalent Bonds (Water Soluble)

6
Basic Carbon Structures Oxygen
7
Carbon Oxygen (Double Bond)

• When a carbon is doubly bound to a oxygen called
  a carbonyl the most common functional
  possibilities are
• Aldehyde C-(CO)-H
• Ketone C-(CO)-C
• Carboxylic Acid C-(CO)-O-H
• Carboxylic Acid Ester C-(CO)-O-C
• Carboxylic Acid Anhydride C-(CO)-O-(CO)-C
• Properties Polar Covalent Bonds (Water Soluble)
• Carboxylic Acid is a strong acid

8
Basic Carbon Structures Carboxyl
9
Carbon Nitrogen

• When a carbon is singly bound to a nitrogen the
  most common functional possibilities are
• Amine- (C-N) single bond
• Imine- (CN) double bond
• Nitrile (CN) triple bond
• Nitro (C-NO2)
• Amide (CO)-N-
• Properties Polar Covalent Bonds (Water Soluble)
• Can be strongly basic (accepts a proton)

10
Basic Carbon Structures Nitrogen
11
Carbon Sulfur

• When a carbon is singly bound to a sulfur the
  most common functional possibilities are
• Thiol (C-S-H) single bond to carbon and one to
  hydrogen
• Sulfide (C-S-C) 2 single bond to carbon(s)
• Sulfoxide C-(SO)-C double bond
• Sulfone C-(OSO)-C 2 double bonds
• Properties Polar Covalent Bonds (Water Soluble)

12
Basic Carbon Structures Sulfur
13
Common Functional Groups
14
Basic Carbon Structures Alkane
15
Basic Carbon Structure Alkene
16
Basic Carbon Structure Alkyne
17
Basic Carbon Structure Alcohol
18
Basic Carbon Structure Ether
19
Basic Carbon Structure Carboxyl

• Carboxyl is found in a number of functional
  groups.
• It is reactive and is often used in organic
  reactions.

20
Basic Carbon Structure Aldehyde
21
Basic Carbon Structure Ketone
22
Basic Carbon Structure Carboxylic Acid
23
Basic Carbon Structure Ester
24
Basic Carbon Structure Amine
25
Basic Carbon Structure Imine
26
Basic Carbon Structure Nitrile
27
Basic Carbon Structure Nitro
28
Basic Carbon Structure Amide
29
Basic Carbon Structure Sulfide
30
Basic Carbon Structure Sulfoxide
31
Basic Carbon Structure Sulfone
32
Basic Carbon Structure Thiol
33
What are Alkanes?

• Alkanes are chains of carbon(s) and hydrogen(s)
  that are SP3 hybridized.
• Remember Carbon and hydrogen maintain similar
  electronegativies so that they have a covalent
  bond (even distrubtion of electrons). Non-polar
  molecules.

34
Properties of Alkanes

• Alkane chains are nonpolar molecules single
  bonded (SP3) carbon chains. You can think of
  them as oils.
• Alkanes are saturated hydrocarbon (also
  aliphatic) because they only contain carbons and
  hydrogens.
• Octane is an alkane chain of 8 carbons and 18
  hydrogens that you use as fuel in your gas tank.
• Cooking oils are also alkane chains.

35
Types of Alkane Chains

• There are two different types of alkane chains.
• 1) Straight chain alkanes (normal alkanes)

2) Branched-chain alkanes
36
Different Structures that Represent Alkanes
All of these structures represents C4H10 butane
37
Alkane Isomers

• Isomers are compounds that have the same number
  and kind of atoms but are arranged differently.
  They can be applied to most organic structures.
• Constitutional Isomers have the same molecular
  formula but have different arrangements. See
  below (C4H10)

They both have the same number of carbons and
hydrogens.
38
Naming Carbon Backbones

• To name carbon chains we determine the number of
  the longest connected carbons to get a proper
  name.
• For example if we had a 5 carbon chain we would
  have Pent-
• And if the carbon chain were all single bonds we
  would have an ane ending.
• The Name would be Pentane

39
Naming Carbons Skeletons

• 1 (Carbon) Meth-
• 2 (Carbons) Eth-
• 3 (Carbons) Prop-
• 4 (Carbons) But-
• 5 (Carbons) Pent-
• 6 (Carbons) Hex-
• 7 (Carbons) Hept-
• 8 (Carbons) Oct-
• 9 (Carbons) Non-
• 10 (Carbons) Dec-

Methane Ethane Propane Butane Pentane Hexane Hepta
ne Octane Nonane Decane
40
Carbons as Substitutents

• If carbon chains are part of a branched alkane
  chain then the branches would be the same parent
  (backbone) name but you would add a yl to the
  end of the name.
• Methyl
• Propyl
• Octyl
• Decyl

41
Naming Carbon Chains (Alkyl)

• Prefix Locant Parent Suffix

What is the primary group functional group.
Additional functional groups and placements.
How many carbons are in the longest chain.
Where is the primary group (number).
42
Steps to Naming Alkane Chains

• Step 1. Find the longest carbon chain (Parent
  hydrocarbon). YOU HAVE TO REALLY LOOK.
• Step 2. Number the atoms in the main chain. Make
  sure that if anything is bound to this chain it
  is at the lowest carbon number.
• Step 3. Identify and number the substitutents.
• Step 4. Write the name as a single word. Use
  hyphens to separate the groups and comma for the
  numbers.
• Step 5. Name a complex substitutents as though it
  were itself compound.

43
Example 1
Find the longest carbon chain By counting carbons.
Number the carbons in the chain substitutents
with the lowest number.
Seven carbons - Hept
Identify the number and name of the
substitutents Methyl on 3 carbon
Write the name on one line 3-Methylheptane
44
Types of Carbons
These are the types of SP3 carbons, Primary,
Secondary, Tertiary, Quaternary carbons.
45
Other Branched Alkane Group Names
46
Properties of Alkanes

• Alkanes are normally chemically inert (normally
  does not easily react with anything except with
  O2)
• Both the melting point and boiling point
  increases with the length of the carbon chain.
• Increased branching decrease the boiling point
  when compared to the straight chains.

47
Conformation of Ethane

• Stereochemistry is the branch of chemistry that
  is concerned with the three dimensional aspects
  of molecules.
• Carbons that are singly bond rotate in space
  (just like an umbrella).

Newman Projections looks directly down the carbon
carbon bond.
48
Torsional Strain

• Torsional Strain describes how atoms or groups
  move between single bonds as they rotate.
• When 2 atoms or groups overlap then the energy
  increases (eclipsed), when they move apart
  (staggered) the energy decreases.
• This happens three times in a rotation of 360o.

49
Conformation Energies

• Energies of Ethane changes not only in the
  staggered and eclipsed forms but with the size of
  the additional groups bound.
• The bigger the groups the more energy it takes
  to pass each other when rotating.
• The lowest energy called the anti-conformation
  places the two bulk groups on the other side of
  the bond.

50
Take Home Message

• Know Functional Groups
• Know Naming of Alkanes
• Know Properties of Alkanes
• Understand Conformation and its Energies.