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<onlyinclude>An '''unsaturated hydrocarbon''' is a type of [[hydrocarbon]] which has at least one double bond, triple bond, or ring in its carbon chain. These molecules will therefore have fewer hydrogen atoms than the maximum the carbon chain could possibly hold (if all bonds were single bonds).</onlyinclude> Molecules that have only single bonds and contain the maximum amount of hydrogen are [[saturated hydrocarbons]]. <ref name="unsat">“Calculating Degree of Unsaturation - Chemistry LibreTexts,” Chemistry LibreTexts, 5-Jun-2019. [Online]. Available: https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Map%3A_Organic_Chemistry_(McMurry)/Chapter_07%3A_Alkenes%3A_Structure_and_Reactivity/7.02_Calculating_Degree_of_Unsaturation. [Accessed: 14-Jun-2019].</ref><br />
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Saturated hydrocarbons have the [[molecular formula]] C<sub>'''''n'''''</sub>H<sub>2'''''n'''''+2</sub>, where '''''n''''' refers to the '''''n'''''umber of carbon [[atom]]s, and can be any natural number. For example: ethane (<chem>C_2H_6</chem>). By contrast, an unsaturated hydrocarbon with '''''n''''' carbon atoms will have ''fewer than n + 2'' hydrogen atoms in its molecular formula. For example: ethene (<chem>C_2H_4</chem>). <br />
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Each ring, or each extra bond added on a single bond (making it a double or triple bond), in an unsaturated hydrocarbon will reduce the number of hydrogen atoms in the molecule by 2, which is referred to as adding one ''degree of unsaturation''.<ref name="unsat"/> You can see this pattern in the molecular formulas for these related hydrocarbons that all have 2 carbon atoms: <br />
* [[Ethane]] - <chem>C_2H_6</chem> - saturated<br />
* [[Ethene]] - <chem>C_2H_4</chem> - unsaturated (one degree of unsaturation)<br />
* [[Ethyne]] - <chem>C_2H_2</chem> - unsaturated (two degrees of unsaturation)<br />
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==Combustion Properties==<br />
The general chemical equation for [[hydrocarbon combustion | combustion]] of a hydrocarbon is: <br />
<center><math>C_xH_y + (x + \frac{y}{4}) O_2 \rightarrow x CO_2 + \frac{y}{2} H_2O </math></center><br />
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Compared to the combustion of [[Saturated_hydrocarbons#Combustion_Properties | saturated hydrocarbons]], unsaturated hydrocarbons will release ''less'' water per molecule of hydrocarbon combusted, and also consume less oxygen. For example, comparing the combustion of one molecule of ethane (<chem>C_2H_6</chem> - saturated) to combustion of one molecule of ethene (<chem>C_2H_4</chem> - unsaturated): <br />
<center>ethane: <math>C_2H_6 + \frac{7}{2} O_2 \rightarrow 2 CO_2 + 3 H_2O </math></center><br />
<center>ethene: <math>C_2H_4 + 3 O_2 \rightarrow 2 CO_2 + 2 H_2O </math></center><br />
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For every mol of ethene combusted, 0.5 mol less oxygen is required, and 1 mol less water is produced compared to ethane. <br />
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There are fewer high-[[chemical energy |energy]] bonds in unsaturated hydrocarbons (compared to saturated hydrocarbons of the same size), unsaturated hydrocarbons will release less energy per molecule when combusted. <ref>"Determination of the Relative Ratio of Unsaturated Fats to Saturated Fats in Nuts Using Bomb Calorimetry", T. Stacey, 2014. [Online]. Available: https://www.mckendree.edu/academics/scholars/issue23/tara-stacey.pdf. [Accessed: 14-Jun-2019].</ref><br />
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==Unsaturated Fats==<br />
The same meaning of ''unsaturated'' used here for hydrocarbons is also used to describe fats and oils, which are [[hydrocarbon derivative]]s. ''Unsaturated'' fats contain carbon chains that are unsaturated (usually containing at least one double bond). Some fats contain several double bonds, and these are called ''polyunsaturated'' fats. The degree of unsaturation affects the melting point of the fat, as well as its health properties. <ref>"Fats and Oils", chem.libretexts.org, 5-Jun-2019. [Online]. Available: https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Book%3A_The_Basics_of_GOB_Chemistry_(Ball_et_al.)/17%3A_Lipids/17.2%3A_Fats_and_Oils. [Accessed 14-Jun-2019].</ref> <br />
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To learn more about this topic, check out the [https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Hydrocarbons/Alkenes Chemistry LibreTexts page] on alkenes (one type of unsaturated hydrocarbon) or [https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Hydrocarbons/Alkynes alkynes], another type of unsaturated hydrocarbon.<br />
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==For Further Reading== <br />
*[[Hydrocarbon combustion]] <br />
*[[Aromatic hydrocarbon]] <br />
*[[Saturated hydrocarbons]]<br />
*Or explore a [[Special:Random|random page]]<br />
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== References ==<br />
<references /></div>energy>Jmdonev