What is actually butane? Linear alkanes

You’ve probably used butane to cook at least once in your life or know someone who has. But what is actually butane?

Perhaps we should talk about alkanes first. An alkane is a compound consisting of hydrogen and carbon only (a hydrocarbon) with all its carbon atoms bonded to four other atoms (that is, saturated). The simplest alkanes have a linear structure. Their linear chain is formed by carbon atoms which are bond to as many hydrogen atoms as necessary to complete the four bonds.

Butane is an alkane with a four-carbon-atom chain. It can be represented:

butane (source)

butane (source)

Methane — main component of natural gas and which humans expel in farts — is an alkane with one only carbon atom.

The formulas of butane and methane are, respectively, CH3−CH2−CH2−CH3 (or C4H10) and CH4. It’s not necessary to represent the bonds between carbon atoms, thus butane would be CH3CH2CH2CH3. Some observation reveals that the numbers of hydrogen atoms equals the double amount of carbon atoms plus two. Therefore, CnH2n + 2 is the general formula for alkanes.

Alkanes are named with a prefix related to the number of carbon atoms in their chain and the ending for alkanes according to each language.

Nomenclature and formulas for some alkanes.

English Catalan Spanish Portuguese extended formula general formula
alkane alcà alcano alcano CnH2n + 2
methane metà metano metano CH4 CH4
ethane età etano etano CH3CH3 C2H6
propane propà propano propano CH3CH2CH3 C3H8
butane butà butano butano CH3(CH2)2CH3 C4H10
pentane pentà pentano pentano CH3(CH2)3CH3 C5H12
hexane hexà hexano hexano CH3(CH2)4CH3 C6H14
heptane heptà heptano heptano CH3(CH2)5CH3 C7H16
octane octà octano octano CH3(CH2)6CH3 C8H18
nonane nonà nonano nonano CH3(CH2)7CH3 C9H20
decane decà decano decano CH3(CH2)8CH3 C10H22

The four first alkanes, from methane to butane, are gases at room temperature and atmospheric pressure. From pentane and to the 17-carbon-atom alkane (heptadecane), they are liquids, and they are solids over 18 carbon atoms at room temperature and atmospheric pressure.


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