Organic Chemistry Notes Mr. B’s Chemistry Hydrocarbons

Hydrocarbons are organic compounds that consist of only C and H atoms. They include the alkanes, alkenes, alkynes, and aromatic hydrocarbons. The main structural difference among hydrocarbon families is the presence of double or triple bonds between carbon atoms. The alkanes are saturated organic compounds, or those with only single bonds. Unsaturated organic compounds are those which have double or triple bonds.

Alkanes

Hydrocarbons having no double or triple bond functional groups are classified as alkanes or cycloalkanes, depending on whether the carbon atoms of the molecule are arranged only in chains or also in rings.

The following table lists the IUPAC names assigned to simple continuous-chain alkanes from C- 1 to C-10. A common "ane" suffix identifies these compounds as alkanes. Longer chain alkanes are well known, and their names may be found in many reference and text books. The names methane through decane should be memorized, since they constitute the root of many IUPAC names. Fortunately, common numerical prefixes are used in naming chains of five or more carbon atoms.

Molecular Structural Molecular Structural Name Isomers Name Isomers Formula Formula Formula Formula methane CH4 CH4 1 hexane C6H14 CH3(CH2)4CH3 5

ethane C2H6 CH3CH3 1 heptane C7H16 CH3(CH2)5CH3 9 propane C3H8 CH3CH2CH3 1 octane C8H18 CH3(CH2)6CH3 18

butane C4H10 CH3CH2CH2CH3 2 nonane C9H20 CH3(CH2)7CH3 35 pentane C5H12 CH3(CH2)3CH3 3 decane C10H22 CH3(CH2)8CH3 75

Alkenes and Alkynes

Alkenes and alkynes are hydrocarbons which respectively have carbon-carbon double bond and carbon-carbon triple bond functional groups. The molecular formulas of these unsaturated hydrocarbons reflect the multiple bonding of the functional groups:

Alkane R–CH2–CH2–R CnH2n+2 This is the maximum H/C ratio for a given number of carbon atoms.

Alkene R–CH=CH–R CnH2n Each double bond reduces the number of hydrogen atoms by 2.

Alkyne R–C≡C–R CnH2n-2 Each triple bond reduces the number of hydrogen atoms by 4.

Functional Groups Functional Group Function-al Family R = carbon group Example Group X=halogen (F, Cl, Br, I) H H H | | | - Carbon, Hydrogen, Alkanes Propane H -C – C – C –H and single covalent bonds only. | | | H H H H H H | | | Alkenes | | Propene = C = C – C – H R – C = C – H | | H H H | Alkynes Propyne  R – C  C – H H – C  C – C – H | H H H H Alkanols | | | Propanol (Alcohols) -OH R – OH H – C – C – C –OH | | | H H H Alkanoic Acids H H O O | | (Carboxylic || Propanoic Acid H – C – C – C = O Acids) -C-OH R – C – OH | | | H H OH Br H H -F fluoro-) | | | Haloalkanes –Cl (chloro-) R X Bromo- – H - C – C – C- H -Br (bromo-) (Alkyl Halides) propane | | | -I (iodo-) (X represents any halogen) H H H

Hydroxyl (Alcohols), Carboxyl (Acids)

There are other names that describe patterns of atoms that are parts of functional groups.

“Hydroxyl” refers to –OH H H 1. The longest carbon chain of 2 Carbons. | | 2. Eth- is root for 2 Carbons; it is an Alkane so –an– is

H-C-C-O-H in the center; -ol is the ending for Hydroxyl alcohols.

| | The base name is Ethanol IUPAC name: Ethanol H H Common name is ethyl alcohol

“Carboxyl” refers to –COOH

1. The longest carbon chain of 2 is circled. 2. Eth- is root for 2 Carbons; it is an Alkane so –an– is in the center;; -oic acid is the ending for a carboxylic acid. The base name is ethanoic acid IUPAC name: ethanoic acid