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A homologous series is a group of compounds that differ by a constant unit, generally a methylene (−CH 2 −) group. The reactants undergo a homologation when the number of a repeated structural unit in the molecules is increased. The most common homologation reactions increase the number of methylene (−CH 2 −) units in saturated chain ...
A homologue (also spelled as homolog) is a compound belonging to a homologous series. [1] Compounds within a homologous series typically have a fixed set of functional groups that gives them similar chemical and physical properties. (For example, the series of primary straight-chained alcohols has a hydroxyl at the end of the carbon chain ...
With their repeated – CH 2 units, the alkanes constitute a homologous series of organic compounds in which the members differ in molecular mass by multiples of 14.03 u (the total mass of each such methylene-bridge unit, which comprises a single carbon atom of mass 12.01 u and two hydrogen atoms of mass ~1.01 u each).
The first few members of the series are gases or liquids at room temperature. The simplest alkene, ethylene (C 2 H 4) (or "ethene" in the IUPAC nomenclature) is the organic compound produced on the largest scale industrially. [5]
Hydrogen, being the lightest existing gas (7% the density of air, 0.08988 g/L at STP), seems to be the most appropriate gas for lifting.It can be easily produced in large quantities, for example with the water-gas shift reaction or electrolysis, but hydrogen has several disadvantages:
The heat content of an ideal gas is independent of pressure (or volume), but the heat content of real gases varies with pressure, hence the need to define the state for the gas (real or ideal) and the pressure. Note that for some thermodynamic databases such as for steam, the reference temperature is 273.15 K (0 °C).
More examples of Homologous series can be added; for instance, homologous series of haloalkanes with the general formula C n H 2n+1-X (where X represents Cl, Br, I), homologous series of aldehydes with the general formula C n H 2n O, homologous series of ketones with the general formula C n H 2n O, where n≥3, homologous series of alkyl ...
The relative activity of a species i, denoted a i, is defined [4] [5] as: = where μ i is the (molar) chemical potential of the species i under the conditions of interest, μ o i is the (molar) chemical potential of that species under some defined set of standard conditions, R is the gas constant, T is the thermodynamic temperature and e is the exponential constant.