Oil, gas and petrochemical products consist of various organic compounds. All of organic compounds share an extraordinary element. Carbon is the element that plays an important role in characterizing these compounds. One vast subset of organic compounds are hydrocarbons. Hydrocarbons exclusively consists of carbon and hydrogen atoms. Other important elements usually exist in organic molecule’s structure are oxygen, sulfur and nitrogen. The characteristics and chemical behaviors of an organic compound is defined by its functional group. In organic chemistry, functional groups are combinations of specific elements connected together in a particular manner. In the following section, we will study some well-known organic compounds and significant functional groups that are so famous in oil and gas industry.

Alkane (Paraffin)

Alkane, traditionally called paraffin, is a saturated hydrocarbon in which all carbon-carbon bonds are single. Their most important commercial sources are either petroleum or natural gas.

Example: Methane (CH4) which is the smallest alkane.

hydrocarbon - a


Alkene (Olefin)

Alkene / (ˈælkiːn) /, traditionally called olefin, is a hydrocarbon that contains carbon-carbon double bond. They can be converted to polyolefin to form polymers.

Example: ethylene, also known as ethene, (C2H4) is the smallest alkene.

hydrocarbon - ethylene



hydrocarbon - butyne

Alkyne / (ˈælkaɪn) / is an unsaturated hydrocarbon containing at least one carbon-carbon triple bond.

Example: Acetylene, also known as ethyne, (C2H2) which has one of the greatest heating value mostly used in welding applications and portable lights.

hydrocarbon - acetylene



Aromatic may refer to every organic compound which has “pi bounds” in resonance with a planar structure. Due to its structure, it has a strong stability.

Example: Benzene (C6H6)

aromatic - organic compound



Aliphatic is a non-aromatic organic compound.

Example: Cyclohexane (C6H12)

aliphatic - organic compound



Naphthene is an aliphatic cyclic saturated hydrocarbon. It consists of only carbon and hydrogen atoms.

Example: Cyclopentane (C5H10)

naphthene - organic compound



In organic chemistry, an alkyl substituent is an alkane missing one hydrogen. Alkyl can be connected to other molecules to form a larger organic compound. The smallest alkyl group is methyl (CH3−).


In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon. Aryl can be connected to other molecules to form a larger organic compound. The simplest aryl group is phenyl (C6H5). Phenyl is derived from benzene by losing one hydrogen atom.


Alcohols are organic compounds with hydroxyl group (-OH). Because of hydroxyl group, they are polar compounds and more water-soluble than simple hydrocarbons. They also tend to have higher boiling point than most hydrocarbons due to the hydrogen bonding.

Example: Methanol, also called methyl alcohol, (CH3OH) is the simplest alcohol.

alcohol functional group


Carboxylic acid

Carboxylic acids are organic acids contain a carboxyl group (C(=O)OH), with R referring to the alkyl group.

Examples: Formic acid, also called methanoic acid, (HCOOH) is the simplest carboxylic acid.

carboxylic acid functional group

Formic acid


Ether functional group consists of an oxygen atom connected to two alkyl or aryl groups with a general formula of (R–O–R′).

Example: Dimethyl ether, also called methoxymethane, (CH3OCH3)  is the simplest ether.

ether functional group

Dimethyl ether


Ketone is a hydrocarbon functional group contains a carbonyl group (R2C=O), where R is a carbon containing substituents.

Example: Acetone (CH3)2CO which is the simplest ketone.

ketone functional group



Aldehyde ia usually created by removing hydrogen from an alcohol. It is a compound containing a functional group with the structure of (−CHO).

Example: Formaldehyde (CH2O) which is the simplest aldehyde. It is mostly used as a precursor to industrial resin and adhesive.

aldehyde functional group



Ester is derived from an acid in which the hydrogen of hydroxyl group (–OH) substitutes by carbon.

Example: Methyl formate, also known as M-formate or methyl methanoate, (C2H4O2) is the simplest ester. It is the methyl ester of formic acid.

ester functional group

Methyl formate


Amide is a compound with the general formula (RC(=O)NR′R″), where R, R’, and R″ represent organic groups or hydrogen atoms. Amide can be converted to polyamide which is a precursor to nylons or proteins.

Example: Formamide, also known as methanamide, (CH3NO) is derived from formic acid.

amide functional group


Thiol (Mercaptan)

Thiol, also called mercaptan, is a sulfur analogue of alcohols. Thiol has a general formula of (R−SH), where R represents an alkyl or other organic molecules. Main characteristic is that they have strong odor. They are also harmful to steel structures and may cause sulfur stress cracking.

Example: Methyl mercaptan. also known as methanethiol (CH3SH)

thiol functional group

Methyl mercaptan


Diol, is a functional group consists of two hydroxyl groups (−OH). An aliphatic diol is also called glycol.

Example: Ethylene glycol (CH2OH)2

Ethylene glycol


Amine is a compound that contains a nitrogen atom with a pair of valance electrons that are not shared with another atom in a covalent bond (unshared pair). Amines are the derivatives of ammonia. They consist of the general formula of (:NRR’R”), where R, R’, and R″ represent organic groups such as an alkyl or aryl. R’ and R” can also be hydrogen atoms. Amines can be both organic and inorganic. Amino acids, which are the building blocks of proteins, contain amines and carboxyl functional groups.

Example: Trimethylamine (TMA) that is an organic amine with a formula of N(CH3)3

amine functional group



In the Bellow table, the most famous hydrocarbon functional groups are provided as a summary.

Functional Group Atomic Structure
Alcohol organic compound
Carboxylic acid organic compound
Ether organic compound
Ketone organic compound
Aldehyde organic compound
Ester organic compound
Amide organic compound
Thiol organic compound
Diol organic compound
Amine organic compound