Octa- prefix

Although hydrocarbons are binary molecular compounds, they are not named like the binary inorganic compounds discussed in Section 2.8. Instead, each alkane has a name that ends in -ane. The alkane with four carbons is called butane. For alkanes with five or more carbons, the names are derived from prefixes like those in Table 2.6. An alkane with eight carbon atoms, for example, is octane (CsHig), where the octa- prefix for eight is combined with the -ane ending for an alkane. 

Stoichiometric Proportions. The stoichiometric proportions of the constituents in a formula may be denoted by Greek numerical prefixes mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- (Latin), deca-, undeca- (Latin), dodeca-,. . . , icosa- (20), henicosa- (21),. . . , tri-conta-(30), tetraconta-(40),. . . , hecta-(100), and so on, preceding without a hyphen the names of the elements to which they refer. The prefix mono can usually be omitted occasionally hemi-(1/2) and sesqui- (%) are used. No elisions are made when using numerical prefixes except in the case of icosa- when the letter i is elided in docosa- and tricosa-. Beyond 10, prefixes may be replaced by Arabic numerals. 

Numbers of ligands are indicated by Greek prefixes di-, tri-, tetra-, penta-, hexa-, hepta-, octa-, nona- (ennea-), deca-, etc. If, however, the names of the ligands themselves already contain these prefixes (e.g., diethyl-enefnamine), the ligand name is placed in parentheses and the prefix outside becomes bis-, tris-, tetrakis-, pentakis-, hexakis-, etc. 

Indicate how many of each element is present with a prefix multiplier (mono = 1 di = 2 tri = 3 tetra = 4 penta = 5 hexa = 6 hepta = 7 octa = 8)... 

Prefix mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca-... 

Nearly all binary molecular compormds involve two nonmetals bonded together. Although many nonmetals can exhibit different oxidation numbers, their oxidation numbers are not properly indicated by Roman numerals or suffixes. Instead, elemental proportions in binary covalent compounds are indicated by using a prefix system for both elements. The Greek and Latin prefixes for one through ten are mono, di, tri, tetra, penta, hexa, hepta, octa, nona, and deca. The prefix mono- is omitted for both elements except in the common name for CO, carbon monoxide. We use the minimum number of prefixes needed to name a compound unambiguously. The final a in a prefix is omitted when the nonmetal stem begins with the letter o we write heptoxide, not heptaoxide. ... 

Some elements form still larger molecules, such as 03 (trioxygen, ozone), P4 (tetraphosphorus), and S8 (octasulfur). The prefixes tri-, tetra-, and octa- mean 3, 4, and 8, respectively. Remember that the molecules of these elements exist only when they are in their pure form or in mixtures, not when they are part of a compound. 

The index lists the names of the chemicals - main entries (upper case), synonyms (lower case), trade names (in italics) etc. - alphabetically. The following prefixes and interpolations are treated as part of the name bis, cycio, iso and the numerical designations mono, di (bi), tri, penta, hexa, octa etc. Cyclopentane will thus be found under c and pentachlorophenol under p in fluorodinitrobenzene, di is part of the name. 

Some pairs of nonmetals form more than one binary molecular compound, and we need to distinguish among them. Generally, we indicate relative numbers of atoms through prefixes mono =, di = 2, tri = 3, tetra = 4, penta = 5, hexa = 6, hepta = 7, octa = 8, nona = 9, deca = 10, and so on. Thus, for the two principal oxides of sulfur we write... 

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