Alkanes, Alkene/Alkyne Nomenclature, and Functional Groups

Alkanes and Their Nomenclature

Structure and Naming of Alkanes

Alkanes are saturated hydrocarbons containing only single bonds between carbon atoms. Their names are based on the number of carbon atoms and the presence of branches or substituents.

• IUPAC Naming: The International Union of Pure and Applied Chemistry (IUPAC) system provides rules for naming organic compounds. For alkanes, the base name reflects the longest continuous chain of carbon atoms.

• Prefix: Indicates the number of carbon atoms (e.g., "hex" for six carbons).

• Suffix: "-ane" denotes an alkane (all single bonds).

• Example: The structure given is CH3-CH2-CH(CH3)-CH2-CH3 which is named 2-methylhexane.

Condensed Structural Formula: For 2,3-dimethyloctane, the condensed formula is written by grouping atoms attached to each carbon:

• Example: CH3CH(CH3)CH(CH3)CH2CH2CH2CH2CH3

General Formula for Alkanes

Alkanes follow the general formula:

• $C_nH_{2n+2}$

• Where n is the number of carbon atoms.

• Example: For 7 carbons, $H = 2(7) + 2 = 16$ hydrogens.

For alkenes (one double bond):

• General formula: $C_nH_{2n}$

• Example: For 5 carbons, $H = 2(5) = 10$ hydrogens.

For alkynes (one triple bond):

• General formula: $C_nH_{2n-2}$

• Example: For 6 carbons, $H = 2(6) - 2 = 10$ hydrogens.

Functional Groups in Organic Chemistry

Identification and Examples

Functional groups are specific groups of atoms within molecules that are responsible for characteristic chemical reactions. Recognizing these groups is essential for understanding organic chemistry.

Structure	Example	Name
C–C	CH3–CH3	Alkane
C=C	CH2=CH2	Alkene
C≡C	CH≡CH	Alkyne
R–X	CH3Cl	Halide (X = halogen)
R–OH	CH3–OH	Alcohol
Ar–OH	(phenol)	Phenol
R–O–R	CH3O–CH3	Ether
R–NH2	CH3–NH2	Amine

• Alkane: Only single bonds between carbons.

• Alkene: Contains at least one double bond.

• Alkyne: Contains at least one triple bond.

• Halide: Contains a halogen atom (F, Cl, Br, I).

• Alcohol: Contains an –OH group attached to a saturated carbon.

• Phenol: Contains an –OH group attached to an aromatic ring.

• Ether: Contains an oxygen atom between two carbon groups.

• Amine: Contains an –NH2 group.

Example Application: Identifying functional groups in a molecule helps predict its reactivity and properties. For instance, alcohols can undergo oxidation, while alkenes can participate in addition reactions.

Summary Table: Hydrocarbon Formulas

Type	General Formula	Example (n=5)
Alkane	$C_nH_{2n+2}$	$C_5H_{12}$
Alkene	$C_nH_{2n}$	$C_5H_{10}$
Alkyne	$C_nH_{2n-2}$	$C_5H_8$

Additional info: The notes also briefly touch on the importance of functional groups in organic chemistry, which is foundational for understanding reactivity and classification of organic compounds.