heneicosane

from The Century Dictionary.

• noun A colorless hydrocarbon, C₂₁H₄₄, found in brown coal paraffin. It melts at 40.4° C., and boils at 215° C. under 15 millimeters pressure.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun organic chemistry Any of very many isomers of the aliphatic hydrocarbon having twenty-one carbon atoms, but especially n-heneicosane CH3(CH2)19CH3