Why are there so many carbon containing compounds?
    1. Carbon can form stable, covalent bonds with other carbon atoms (catenate).
    2. Carbon can form stable bonds with other elements.
    3. Carbon can form double and triple bonds with other carbon atoms or other elements.
    4. Carbon can bond with itself either as straight chains or cyclic compounds with branching possible in either case.

Two different organic compounds can also have the same number of carbon atoms.  These are called isomers.  Isomers are molecules that have the same molecular formulas but different structures and thus different physical and chemical characteristics.  An example of isomerism is butane and 2-methylpropane.  Both have the same molecular formula, C₄H₁₀, but differing physical and chemical properties.

Contrasts Between Organic and Inorganic Molecules
Carbon bonds are almost always covalent. Covalent compounds are often referred to as molecules.
Most bonds between a metal and a nonmetal are ionic. Many inorganic compounds are ionic compounds.

Ionic bonds:
    1. result from the transfer of atoms and not sharing.
    2. are electrostatic.
    3. result with formation of large lattice crystals of cations and anions.
    4. often dissolve in water to give electrolytic solutions (i.e., they conduct electricity).

Classification of Organic Compounds
All organic compounds be generally classified as hydrocarbons (molecules containing only hydrogen and carbon) or substituted hydrocarbons (molecules having one or more hydrogen atoms replaced by another atom or group of atoms).

Hydrocarbons can be further subdivided into Aliphatic (Greek aleiphat "fat") and Aromatic.

Aliphatic can be divided into alkanes, alkenes, and alkynes.

Alkanes are saturated hydrocarbons.  Saturated means that the hydrocarbon has only single bonds and that the hydrocarbon contains the maximum number of hydrogen atoms for each carbon atom.  Unsaturated hydrocarbons contain multiple bonding and contain less than the maximum number of hydrogens per carbon.

Ethane, C₂H₆, is an alkane and is an example of a saturated hydrocarbon.

Ethene, C₂H₄, is an alkene and is an example of unsaturated hydrocarbon.

Ethyne, C₂H₂, is an alkyne and is also an example of unsaturated hydrocarbon.

Aromatic compounds are unsaturated hydrocarbons and contain a benzene ring.

Functional Group	Name	Family of Organic Compounds	Example
	carbon-carbon double bond	Alkene	1-Butene
	carbon-carbon triple bond	Alkyne	1-Butyne
	Benzene ring	Aromatic	Toluene
	Halogen atom  (-X)	Alkyl halide	Chloromethane CH3Cl
	Hydroxyl group  (-OH)	Alcohol	Ethanol CH3CH2OH
	Alkoxy group  (-OR)	Ether	Dimethyl ether CH3-O-CH3
	Carbonyl group	Aldehyde or ketone	Ethanal
	Carboxyl group	Carboxylic acids	Acetic acid
	Acyl group	Carboxylic acid derivatives	Methyl acetate
	Amino group	Amines	Methyl amine

Alkanes
Alkanes are saturated hydrocarbons. This means that contain only carbon and hydrogen atoms bonded by single bonds only.
The general formula for an alkane is C_nH_2n+2. In this formula, n, is the number of carbon atoms in the molecule.
The molecular formula is the actual ratio of atoms to one another in a molecule.
    A structural formula represents a structure and emphasizes the bond connection between atoms.
    A condensed formula is a simplification of the structural formula.
    A line formula is a simplified representation of a structural formula in which many of the C-H bonds are not shown.
        In a line formula, the carbons are understood to exist at the vertices of each of the angles and the number of
        hydrogens necessary are also understood, though not written.
 

Alkane	Molecular Formula	Structural Formula	Condensed Formula	Line Formula
Propane	C3H8		CH3CH2CH3
Butane	C4H10		CH3CH2CH2CH3

Names and Formulas of the First Ten Straight-Chain Alkanes & Alkyl Groups

Name	Molecular Formula	Condensed Formula	Alkyl group	R-
Methane	CH4	CH4	methyl	CH3-
Ethane	C2H6	CH3-CH3	ethyl	CH3-CH2-
Propane	C3H8	CH3-CH2-CH3	propyl	CH3-CH2-CH2-
Butane	C4H10	CH3-CH2-CH2-CH3	butyl	CH3CH2CH2CH2-
Pentane	C5H12	CH3CH2CH2CH2CH3 or CH3-(CH2)3-CH3	pentyl	CH3-(CH2)3-CH2-
Hexane	C6H14	CH3-(CH2)4-CH3	hexyl	CH3-(CH2)4-CH2-
Heptane	C7H16	CH3-(CH2)5-CH3	heptyl	CH3-(CH2)5-CH2-
Octane	C8H18	CH3-(CH2)6-CH3	octyl	CH3-(CH2)6-CH2-
Nonane	C9H20	CH3-(CH2)7-CH3	nonyl	CH3-(CH2)7-CH2-
Decane	C10H22	CH3-(CH2)8-CH3	decyl	CH3-(CH2)8-CH2-

Hydrocarbon carbon bonding characteristics:
Carbon always forms 4 bonds with no lone pair electrons on the carbon atom. (One exception of this is carbon monoxide.)
Single bonded carbon atoms have bond angles of 109.5^o.  Alkanes are composed of carbon atoms that have tetrahedral geometry.  Any compound with carbon having four single bonds will have a tetrahedral shape about any of the single bonded carbon atoms, with the bonded atoms at the vertices of a tetrahedron.

Hydrocarbon physical characteristics:
Hydrocarbons are nonpolar. They are immiscible with water.
They have relatively low melting points and boiling points. The first four alkanes (methane – butane) are all gases at room temperature.
Hydrocarbons are generally less dense than water.
Compounds that differ only in the number of -CH₂- groups inserted in the carbon chain form a family group called a homologous series.
Members of this family are called homologs.
Members of a homologous series are very similar in their chemical reactivity.
As more carbons are added and the size of the molecule increases, they exhibit gradually changing physical properties.
As number of carbon atoms increases (increase in molecular weight) the melting points and boiling points.
Except for the very small alkanes, the boiling point rises 20 to 30 degrees for each carbon that is added to the chain.
The first four alkanes (i.e. with fewer than 5 carbons) are gases at room temp.

Alkyl groups
When a hydrogen is removed from a hydrocarbon, the resulting fragment is called an alkyl group. The name of the alkyl group is derived from the alkane by removing the –ane and replacing with –yl. An alkyl group can be represented by "R" in chemical structures.

Alkane	Condensed Lewis Structure	Alkyl group	R-
Methane	CH4	methyl	CH3-
Ethane	CH3-CH3	ethyl	CH3CH2-
Propane	CH3-CH2-CH3	propyl	CH3CH2CH2-
Butane	CH3-CH2-CH2-CH3	butyl	CH3CH2CH2CH2-
Pentane	CH3CH2CH2CH2CH3	pentyl	CH3CH2CH2CH2CH2-

Carbon atoms are classified by the number of other carbon atoms bonded to it.
A primary carbon (1^o) is bonded to one carbon.
A secondary carbon (2^o) is bonded to two carbons.
A tertiary carbon (3^o) is bonded to three carbons.
A quaternary carbon (4^o) is bonded to four carbons.

Alkyl groups are classified according to the number of carbons attached to the carbon that joins the alkyl group to the molecule.

primary alkyl group	secondary alkyl group	tertiary  alkyl group

Hydrogen atoms are classified according to the type of carbon to which they are attached and are given equivalent names.
Primary = connected to a primary carbon.
Secondary = connected to a secondary carbon.
Tertiary = connected to a tertiary carbon.

Remove a primary hydrogen from propane and the resulting alkyl group is the normal propyl group or n-propyl group.
n-propyl CH₃CH₂CH₂-

Remove a secondary hydrogen from propane and the resulting alkyl group is a isopropyl group.
isopropyl (CH₃)₂CH-

The alkyl groups the butanes, C₄H₁₀, are n-butyl, sec-butyl,  iso-butyl, and tert-butyl.

Nomenclature of Alkanes
A chemical name has three parts in the IUPAC system: Prefix, Parent,  Suffix.
    Prefix gives the location.
    Parent or stem tells how many carbons.
    Suffix identifies the functional group.

I.U.P.A.C. Nomenclature of Alkanes
1.  Determine the parent compound find the longest continuous chain of carbon atoms. If two different chains of equal length are present, choose the one with the larger number of branch points.

2.  Name and number the atoms. The stem name is derived from the parent hydrocarbon.

3.  Number the parent chain to give the lowest number to the carbon bonded to the first group encountered on the parent chain.

4.  If the same substituent occurs more than once, the number of each carbon of the parent alkane to which it is attached is given, and the number of substituent groups involved is indicated by prefix such as di-, tri, tetra-, and so on.

5.  Name the compound, beginning with the side chains in alphabetical order and ending with the name of the parent compound. Follow these rules:
    a.   Always use commas between numbers.
    b.   Always use hyphens between numbers and words.
    c.   Do not leave spaces in the name.
    d.   When alphabetizing substituent groups, ignore the prefixes, di-, tri-, and so on.
    e.   Use the lowest possible numbers.

Constitutional isomers
Isomers are compounds with identical molecular formulas but which differ in the atomic arrangements.  These compounds differ in shape and properties and are actually different compounds.  Constitutional isomers are molecules having the same molecular formula but different arrangement of atoms (e.g., n-butane and 2-methylpropane).   Geometric isomers are molecules which have the same molecular formula but differing spatial arrangement of atoms due to absence of free rotation.

There are 2 butane, C₄H₁₀, isomers.
There are 3 pentane, C₅H₁₂, isomers.
There are 4 hexane, C₆H₁₄, isomers.
There are 9 heptane, C₇H₁₆, isomers.
There are 18 octane, C₈H₁₈, isomers.
There are 35 nonane, C₉H₂₀, isomers.
There are 75 decane, C₁₀H₂₂, isomers.

Cycloalkanes
The cycloalkanes have the general formula of C_nH_2n.

Cyclopropane C3H6

Cyclobutane C4H8

Cyclopentane C5H10

Cyclohexane C6H12

Cycloheptane C7H14

I.U.P.A.C. Nomenclature of Cycloalkanes
1. Count the number of carbon atoms in the ring and the number in the largest substituent. If the number of carbon atoms in the ring is equal to or greater than the number in the largest substituent, the compound in named as an alkyl-substituted cycloalkane. If the number of carbon atoms in the largest substituent is greater than the number in the ring, the compound is named as a cycloalkyl-substituted alkane.

2. For alkyl-substituted cycloalkanes, start at a point of attachment and number the substituents on the ring so as to arrive at the lowest sum.
    a.  Number substituents alphabetically.
    b. Halogen are treated exactly like alkyl groups.

3. Use hyphen after cis or trans.

Cis-Trans Isomerism in Cycloalkanes
Rotation around the bonds in a cyclic structure is limited. The formation of cis-trans isomers or geometric isomers, is a consequence of the absence of the free rotation. Geometric isomers are a type of stereoisomer.  The term "cis" is derived from Latin and means "on the same side."  The term "trans" is also derived from Latin and means "across from."

Conformations of Alkanes and Cycloalkanes
Because there is free rotation around a carbon-carbon single bond, even a very simple alkane like ethane, can exist in an unlimited number of forms.  Cycloalkanes (except cyclopropane) also exist in different conformations.  Cyclohexane exist in a "chair conformation" (the most energetically favorable) or a "boat conformation."   The hydrogen atoms which lie above or below the ring are said to be axial.   Those that lie roughly in the plane of the ring are called equatorial.   When the chair form "flips", the six equatorial hydrogens become axial and vice versa for the six axial.

The axial hydrogens are actually quite crowded. If one of them is replaced by a larger group, even one as small as a methyl group, the chair form in which the larger substituent is equatorial is strongly favored. This minimizes the crowding, resulting in a more stable structure.

The boat conformation is less stable than the chair because the hydrogen atoms are not perfectly staggered.

Reactions of Alkanes and Cycloalkanes
Combustion
Hydrocarbons react with an excess of oxygen to yield carbon dioxide and water.
    CH₄ + 2 O₂ --> CO₂ + 2 H₂O + Heat
    2 C₂H₆ + 7 O₂ --> 4 CO₂ + 6 H₂O + Heat

If alkanes are burned with insufficient oxygen then carbon monoxide is formed instead of carbon dioxide.
    2 CH₄ + 3 O₂ --> 2 CO + 4 H₂O + Heat (?)
    2 C₂H₆ + 5 O₂ --> 4 CO + 6 H₂O

Halogenation
Halogenation is a substitution reaction.  Substitution reactions involve replacement of an atom with another atom or group of atoms.  In halogenation, hydrogens in the hydrocarbon are substituted with a halogen (Cl or Br).  The product of a halogenation is an alkyl halide (RX) and hydrogen halide.
                           light or heat (200-400^oC)
        R-H + X₂ -------------------------> R-X + HCl
X₂ represents either Cl₂ or Br₂.  [Iodine, I₂, does not work.]
Tertiary hydrogens (3^o ) are replaced more rapidly than secondary ( 2^o) which react faster than primary (1^o ).

If the halogenation reaction is allowed to continue, the alkyl halide can react with halogen atoms and more than one product can be formed, resulting in a mixture of products.
    CH₄ + Br₂ --> CH₃Br + HBr
    CH₃Br + Br₂ --> CH₂Br₂ + HBr
    CH₂Br₂ + Br₂ --> CHBr₃ + HBr
    CHBr₃ + Br₂ --> CBr₄ + HBr

n-propane + Cl₂/light ---> 1-chloropropane + 2-chloropropane
                                                          45%                         55%

n-butane + Cl₂/light ---> 1-chlorobutane + 2-chlorobutane
                                                    28%                         72%

isobutane + Cl₂/light  ---> 1-chloro-2-methylpropane + 2-chloro-2-methylpropane
                                                                                                                 64%

Chlorination gives mixtures in which no isomer greatly predominates; in bromination, by contrast, one isomer may predominate to such an extent as to be almost the only product, making up 97-99% of the total mixture.

Bromination of the same alkanes above results with the more substituted carbon being the site of bromination with only trace amounts of the other possibilities.