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