Quiz on Wednesday

Study:

• Difference between aliphatic and aromatic
• Difference between alkanes, alkenes, alkynes
• What is a organic compound
• What is unique about carbon
• Nomenclature

Hydrocarbons

What are hydrocarbons?

• The simplest aliphatic and aromatic compounds
• Only contain hydrogen and carbon
• Can contain single, double, or triple bonds
• Classified by the types of bonds.

Alkanes

• Alkanes are aliphatic hydrocarbons that only contain single bonds.
• The general formula for alkanes is C_nH_2n+2
• Example: CH₄, C₂H₆, C₃H₈
• Considered saturated because carbon is surrounded by the max number of hydrogen.
• Methane is the simples alkane (CH4)
• Each consecutive alkane adds a carbon and its respective hydrogens.
• Methane: 1 carbon
• Ethane: 2 carbons
• Propane: 3 carbon
• Butane: 4 carbons
• Properties of Alkanes
• Very low melting and boiling points. They rise as carbons are added.
• Ex. methane
• Melting point (C):  -183
• Boiling point (C): -164
• Non-polar

Alkenes

• Hydrocarbons that contain double bonds between carbon atoms
• Contain the prefix -ene.
• The smallest is ethene. Why not methene?
• Considered unsaturated, because the double bond prevents the max number of hydrogen from bonding.
• Naming of alkenes requires numbering the carbons to identify the place where the double bond is.
• You start at the carbon that will give you the smallest number.
• This allows us to know where the double bond is. 
• Properties of Alkenes:
• Slightly higher melting/boiling points
• The first couple are gases at room temperature
• Relatively non polar

Alkynes

• Hydrocarbons that contain triple bonds between the carbon atoms
• Uses the prefix -yne
• The simplest is the most common, ethyne (acetylene).

Cyclic Aliphatic Compounds

• Not all hydrocarbons are open chains of carbon atoms.
• Some form a ring.
• 5 and 6 alkane rings are most abundant. 
• Some can have more than one double bond.

Aromatic Structures

• All contain a form of a molecule benzene
• They are called aromatic because they often smell good
• C₆H₆ is the simplest aromatic compound known
• It was hard to figure out the structure:
• Behaves like an alkane, but they knew from the molecular weight that it had several double and triple bonds.
• When they measured the bond length, the found that it should contain 1.5 bond lengths.
• Showed that carbon was in a ring and all had identical bonds
• In 1865, August Kekule proposed the structure. 
• He said that it was a dynamic equilibrium of the two.
• The double bonds were not “tied dow”, but are more or less shared.

Organic Chemistry Introduction

• Organic Compounds: covalently bonded carbon compounds, with the exception of carbonates, carbon oxides, and carbides.
• Biochemistry: the study of complex reactions taking place between organic compounds within living organisms.

Unique Carbon Atom

• Carbon has some unique properties that enable it to form hundreds of thousands of compounds.
• Carbon has 4 valence electrons, requiring 4 bonds to obtain an octet
• Carbon forms strong chemical bonds with other carbon atoms
• Carbon forms stable, almost non polar bonds with hydrogen
• Carbon atoms can bond to a wide variety of atoms
• H, P, O, N, S, the halogens, and even metal atoms.
• Bonds can be straight, branched, and in various lengths.
• They can even form rings
• Can form double and triple bonds

Structural Forumlas

• Structural formulas are used a lot in organic chemistry because molecular formulas can mean various compounds. 
• C₂H₆O can mean ethanol or dimethyl ether
• See page 446 in your books

Classification

• There are approx. 300,000 new organic compounds synthesized for the first time every year.
• It is important to have some categories:
• Aliphatic compounds: without a benzene ring
• Aromatic compounds: with a benzene ring