{"id":10102,"date":"2016-08-26T08:21:04","date_gmt":"2016-08-26T12:21:04","guid":{"rendered":"https:\/\/www.masterorganicchemistry.com\/?p=10102"},"modified":"2026-04-22T10:02:53","modified_gmt":"2026-04-22T15:02:53","slug":"degrees-of-unsaturation-index-of-hydrogen-deficiency","status":"publish","type":"post","link":"https:\/\/www.masterorganicchemistry.com\/2016\/08\/26\/degrees-of-unsaturation-index-of-hydrogen-deficiency\/","title":{"rendered":"Degrees of Unsaturation (or IHD, Index of Hydrogen Deficiency)"},"content":{"rendered":"<p><strong>Degrees of Unsaturation (Index Of Hydrogen Deficiency)<\/strong><\/p>\n<ul>\n<li>The molecular formula of a compound can give clues about its structure.<\/li>\n<li>The formula for an <strong>alkane<\/strong> follows the pattern C<sub>n<\/sub>H<sub>n+2<\/sub>\u00a0 where n is the number of carbons.<\/li>\n<li>Every pi bond or ring reduces the number of hydrogens by 2.<\/li>\n<li>Therefore the molecular formula can tell us the number of pi bonds or rings in an unknown structure.<\/li>\n<li>This is called the\u00a0<strong>index of hydrogen deficiency (IHD)\u00a0<\/strong>or degrees of unsaturation.<\/li>\n<li>The full formula has modifications that account for halogens and nitrogens<\/li>\n<\/ul>\n<p><img fetchpriority=\"high\" decoding=\"async\" class=\"alignnone wp-image-15407\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/0-summary-for-index-of-unsaturation-formula-degrees-of-unsaturation-carbon-hydrogen-nitrogen-halogens.gif\" alt=\"summary for index of unsaturation formula degrees of unsaturation carbon hydrogen nitrogen halogens\" width=\"630\" height=\"377\" \/><\/p>\n<p><strong>Table of Contents<\/strong><\/p>\n<ol>\n<li><a href=\"#one\">What&#8217;s So Great About The IHD?<\/a><\/li>\n<li><a href=\"#two\">Playing Around With Molecular Formulae: Degrees of Unsaturation<\/a><\/li>\n<li><a href=\"#three\">For A Hydrocarbon With No Rings Or Double Bonds The Number Of Hydrogens Is Equal To Twice The Number Of Carbons, Plus 2<\/a><\/li>\n<li><a href=\"#four\">Each Double Bond or Ring Reduces The Hydrogen Count By 2<\/a><\/li>\n<li><a href=\"#five\">Each Ring Or Double Bond Is Called A &#8220;Degree Of Unsaturation&#8221;<\/a><\/li>\n<li><a href=\"#six\">Example: Benzene (4 Degrees Of Unsaturation)<\/a><\/li>\n<li><a href=\"#seven\">What About Molecules Containing Oxygen?<\/a><\/li>\n<li><a href=\"#eight\">\u00a0What About Halogens?<\/a><\/li>\n<li><a href=\"#nine\">Nitrogen Is A Little Bit Tricky<\/a><\/li>\n<li><a href=\"#ten\">A Unified Formula For Degrees of Unsaturation<\/a><\/li>\n<li><a href=\"#eleven\">Applying The IHD Formula To Four Real-Life Examples<\/a><\/li>\n<li><a href=\"#quiz\"><span class=\"s1\">Quiz Yourself!<\/span><\/a><\/li>\n<\/ol>\n<hr \/>\n<h2><a id=\"one\"><\/a>1. What&#8217;s So Great About The IHD?<\/h2>\n<p>The best thing about the IHD is that it is an easy equation to use that gives you useful information about the structure of an unknown compound. It literally takes a minute to do.\u00a0<strong>Calculating the degrees of unsaturation is THE first task I recommend doing when you are faced with determining the structure of an unknown compound with a known molecular formula.\u00a0<\/strong><a href=\"https:\/\/www.masterorganicchemistry.com\/2016\/08\/23\/structure-determination-case-study-deer-tarsal-gland-pheremone\/\">In this post<\/a>, we see that this calculation was clutch in the determination of the structure of the side chain of deer tarsal pheromone.<\/p>\n<p>Before we get going,\u00a0see if you can apply the equation in the box above to\u00a0find the degrees of unsaturation in\u00a0these\u00a0<em>extremely<\/em> well known molecules whose formulae are given below.<\/p>\n<ul>\n<li>C<sub>9<\/sub>H<sub>8<\/sub>O<sub>4<\/sub><\/li>\n<li><span title=\"Carbon\">C<sub>21<\/sub><span title=\"Hydrogen\">H<\/span><sub>30<\/sub><span title=\"Oxygen\">O<\/span><sub>2<\/sub><\/span><\/li>\n<li><span title=\"Carbon\">C<\/span><sub>17<\/sub><span title=\"Hydrogen\">H<span style=\"font-size: small;\"><span style=\"line-height: 20px;\">21<\/span><\/span><\/span><span title=\"Nitrogen\">N<\/span><span title=\"Oxygen\">O<span style=\"font-size: small;\"><span style=\"line-height: 20px;\">4<\/span><\/span><\/span><\/li>\n<li><span title=\"Carbon\">C<\/span><sub>11<\/sub><span title=\"Hydrogen\">H<\/span><sub>15<\/sub><span title=\"Nitrogen\">N<\/span><span title=\"Oxygen\">O<\/span><sub>2<\/sub><\/li>\n<\/ul>\n<p>The latter three molecules are somewhat &#8220;naughty&#8221; examples, being illegal in most, if not all states. Hopefully that&#8217;s an incentive for you to actually do the calculation!\u00a0 (answers at the bottom of the post).<\/p>\n<h2><strong><a id=\"two\"><\/a>2. Playing Around With Molecular Formulae: Degrees of Unsaturation<\/strong><\/h2>\n<p><strong>\u00a0<\/strong>Let&#8217;s start this discussion by looking for patterns in molecular formulae.\u00a0We&#8217;ll start with hydrocarbons containing no double bonds or rings.<\/p>\n<p>Can you see a relationship between\u00a0the number of carbons and the number of hydrogens?<\/p>\n<p>More specifically, can you come up with a formula?<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-15408\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/1-hydrocarbons-with-no-rings-or-multiple-bonds-have-the-formula-number-of-hydrogens-equals-2-times-number-of-carbons-plus-2.gif\" alt=\"hydrocarbons with no rings or multiple bonds have the formula number of hydrogens equals 2 times number of carbons plus 2\" width=\"600\" height=\"290\" \/><\/p>\n<h2><a id=\"three\"><\/a>3. For A Hydrocarbon With No Rings Or Double Bonds The Number Of Hydrogens Is Equal To Twice The Number Of Carbons, Plus 2<\/h2>\n<p>You should be able to see that for a hydrocarbon with no rings or double bonds, <strong>the number of hydrogens is equal to twice the number of carbons, plus 2.<\/strong><\/p>\n<p>So for a molecule like dodecane (C<sub>12<\/sub>) we&#8217;d expect to see (12 x 2) + 2 = <strong>26 hydrogens.<\/strong><\/p>\n<p>Now: what happens to the molecular formula when we add a double bond to the molecule?<\/p>\n<p><img decoding=\"async\" class=\"alignnone wp-image-15409\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/2-index-of-hydrogen-deficiency-effect-of-doubld-bonds-on-hydrogen-count-each-double-bond-reduces-it-by-2.gif\" alt=\"index of hydrogen deficiency effect of doubld bonds on hydrogen count each double bond reduces it by 2\" width=\"600\" height=\"350\" \/><\/p>\n<h2><a id=\"four\"><\/a>4. Each Double Bond or Ring Reduces The Hydrogen Count By 2<\/h2>\n<p>You should be able to see that each multiple bond (\u03c0 bond ) the number of hydrogens in the formula decreases by two. Ethyne (2 \u03c0 bonds) has two fewer hydrogens than ethene (1 \u03c0 bond), which has two fewer hydrogens than ethane (zero \u03c0 bonds).<\/p>\n<p>Hydrocarbons containing \u00a0\u03c0 bonds are often called &#8220;unsaturated&#8221; hydrocarbons. They can be treated with hydrogen (<a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/04\/02\/alkene-addition-pattern-3-the-concerted-pathway\/\">Pd\/C, H<sub>2<\/sub><\/a>\u00a0) to give the corresponding alkane with no \u00a0\u03c0 bonds, which is then said to be &#8220;saturated&#8221; with hydrogen. (Compare &#8220;<a href=\"https:\/\/en.wikipedia.org\/wiki\/Unsaturated_fat\" target=\"_blank\" rel=\"noopener noreferrer\">unsaturated fats<\/a>&#8220;, which contain alkenes, and &#8220;<a href=\"https:\/\/en.wikipedia.org\/wiki\/Saturated_fat\" target=\"_blank\" rel=\"noopener noreferrer\">saturated fats<\/a>&#8221; which do not).<\/p>\n<p>Since every pi bond results in a loss of 2 hydrogens from the molecular formula, we refer to this to as a &#8220;<strong>degree of unsaturation<\/strong>&#8220;.<\/p>\n<p>Let&#8217;s turn our attention to cyclic compounds. Do you notice a similar effect?<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15410\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/3-index-of-hydrogen-deficiency-index-of-unsaturation-each-ring-reduces-number-of-hydrogens-by-two.gif\" alt=\"index of hydrogen deficiency index of unsaturation each ring reduces number of hydrogens by two\" width=\"600\" height=\"532\" \/><\/p>\n<p>You should! Every ring in the molecule decreases the number of hydrogens by two.<\/p>\n<h2><a id=\"five\"><\/a>5. Each Ring Or Double Bond Is Called A &#8220;Degree Of Unsaturation&#8221;<\/h2>\n<p>Therefore,<strong> each ring introduces a &#8220;degree of unsaturation&#8221; into the molecule.\u00a0<\/strong><\/p>\n<p>You might ask: what if we have a molecule with rings <em>and<\/em> multiple bonds?\u00a0See for yourself.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15411\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/4-effect-of-double-bonds-and-rings-on-number-of-hydrogens-degrees-of-unsaturation-the-effect-is-additive.gif\" alt=\"effect of double bonds and rings on number of hydrogens degrees of unsaturation the effect is additive\" width=\"630\" height=\"448\" \/><\/p>\n<p><strong>The effect is additive.<\/strong> That is, the &#8220;degrees of unsaturation&#8221; is the\u00a0<strong>sum<\/strong> of the number of double bonds and rings.<\/p>\n<p>Note that it doesn&#8217;t tell you how many double bonds are present or how many rings are present. <strong>It merely tells you their sum<\/strong>.<\/p>\n<h2><strong><a id=\"six\"><\/a>6. Example: Benzene (4 Degrees Of Unsaturation)<\/strong><\/h2>\n<p>For instance, thus the molecular formula C<sub>6<\/sub>H<sub>6<\/sub> (4 degrees of unsaturation) is satisfied by molecules with<\/p>\n<ul>\n<li>4 pi bonds<\/li>\n<li>3 pi bonds and a ring (<strong>benzene<\/strong>)<\/li>\n<li>two pi bonds and two rings (the very unstable <a href=\"https:\/\/en.wikipedia.org\/wiki\/Dewar_benzene\">Dewar Benzene<\/a>, synthesized in 1963)<\/li>\n<li>one pi bond and three rings (the even more unstable <a href=\"https:\/\/en.wikipedia.org\/wiki\/Benzvalene\">benzvalene<\/a>, a contact explosive, synthesized in 1971)<\/li>\n<li>and yes, even zero pi bonds and four rings (<a href=\"https:\/\/en.wikipedia.org\/wiki\/Prismane\">prismane<\/a>, synthesized in 1973).<\/li>\n<\/ul>\n<p><span style=\"color: #993366;\"><em>[Historical side note: the formula of benzene was known to be C<sub>6<\/sub>H<sub>6<\/sub> from Michael Faraday in 1825, but the correct\u00a0structure was not proposed until 1865 (<a style=\"color: #993366;\" href=\"https:\/\/en.wikipedia.org\/wiki\/August_Kekul\u00e9\">Kekule<\/a>) and not\u00a0confirmed until 1929, by Catherine Lonsdale&#8217;s X-ray studies . Just a reminder that knowing the molecular formula only gets you so far. ]<\/em><\/span><\/p>\n<p>Helpful hint: if you see 4 degrees of unsaturation in an unknown molecule, thinking &#8220;benzene ring&#8221; is a good place to start.<\/p>\n<h2><a id=\"seven\"><\/a>7. What About Molecules Containing Oxygen?<\/h2>\n<p>So far, so good.\u00a0\u00a0Let&#8217;s move on.\u00a0What about molecules with oxygen?<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15412\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/5-what-is-effect-of-oxygen-and-sulfur-on-index-of-hydrogen-deficiency-formula-they-have-no-effect-on-degrees-of-unsaturation.gif\" alt=\"what is effect of oxygen and sulfur on index of hydrogen deficiency formula they have no effect on degrees of unsaturation\" width=\"600\" height=\"434\" \/><\/p>\n<p>The same rules apply! We can calculate the number of hydrogens from the number of carbons as if the oxygen didn&#8217;t exist.<\/p>\n<p>Note that a \u03c0 bond which contains oxygen still counts as a &#8220;degree of unsaturation&#8221; (see formaldehyde, CH<sub>2<\/sub>O).<\/p>\n<h2><a id=\"eight\"><\/a>8. What About Halogens?<\/h2>\n<p>OK. What about halogens like chlorine, fluorine, iodine and bromine?<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15413\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/6-informula-for-degrees-of-unsaturation-halogens-have-same-effect-as-hydrogens.gif\" alt=\"informula for degrees of unsaturation halogens have same effect as hydrogens\" width=\"600\" height=\"338\" \/><\/p>\n<p>For the purposes of our formula relating hydrogens to carbons for molecules without rings or double bonds,\u00a0<strong>halogens can be counted as hydrogens.\u00a0<\/strong>That is, carbon tetrachloride (CCl<sub>4<\/sub>) has the same degrees of unsaturation (zero) as CH<sub>4<\/sub>.<\/p>\n<p>We can thus modify the equation for a molecule with no double bonds or rings as follows:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15414\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/7-for-compound-with-no-double-bonds-or-rings-equation-for-index-of-hydrogen-deficiency-index-of-unsaturation-formula-is-hydrogens-plus-halogens-equals-2-times-number-of-carbons-plus-2.gif\" alt=\"for compound with no double bonds or rings equation for index of hydrogen deficiency index of unsaturation formula is hydrogens plus halogens equals 2 times number of carbons plus 2\" width=\"600\" height=\"96\" \/><\/p>\n<h2><strong><a id=\"nine\"><\/a>9. Nitrogen Is A Little Bit Tricky<\/strong><\/h2>\n<p>We&#8217;ve saved nitrogen for last, because it&#8217;s a bit weird.\u00a0\u00a0Try to\u00a0see the pattern of how nitrogen affects our formula.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15415\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/8-nitrogen-in-the-formula-for-index-of-unsaturation-is-a-special-case-nh3-has-zero-degrees-of-unsaturation-this-figure-shows-many-examples-of-nitrogen-compounds.gif\" alt=\"nitrogen in the formula for index of unsaturation is a special case nh3 has zero degrees of unsaturation this figure shows many examples of nitrogen compounds\" width=\"600\" height=\"398\" \/><\/p>\n<p>OK, you might have noticed that <em>we can&#8217;t ignore nitrogen like we did oxygen<\/em>.<\/p>\n<p>The way to make the equation work with nitrogen is to add the nitrogen count to the right hand side of the equation, like this:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15416\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/9-formula-for-compound-with-no-double-bonds-or-rings-formula-for-index-of-hydrogen-deficiency-is-here-try-cadaverine-c5h14n2.gif\" alt=\"formula for compound with no double bonds or rings formula for index of hydrogen deficiency is here try cadaverine c5h14n2\" width=\"600\" height=\"77\" \/><\/p>\n<p>Try it with cadaverine (C<sub>5<\/sub>H<sub>14<\/sub>N<sub>2<\/sub>) which contains no double bonds or rings.<\/p>\n<h2><a id=\"ten\"><\/a>10. A Unified Formula For Degrees of Unsaturation<\/h2>\n<p>So far our equation has only applied to &#8220;saturated&#8221; compounds with no double bonds or rings.<\/p>\n<p>How can we use this to make a general formula for &#8220;degrees of unsaturation&#8221;, which is actually&#8230; useful?<\/p>\n<p>Math time. If we move the left hand side over to the right, we get this:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15417\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/10-modified-formula-for-index-of-hydrogen-deficiency-incorporating-carbon-nitrogen-hydrogen-and-halogens.gif\" alt=\"modified formula for index of hydrogen deficiency incorporating carbon nitrogen hydrogen and halogens\" width=\"600\" height=\"42\" \/><\/p>\n<p>Zero equals the degrees of unsaturation in this case.<\/p>\n<p>If we introduce a double bond or ring, the equation will return &#8220;2&#8221;.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15418\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/11-compound-with-1-degree-of-unsaturation-will-return-value-of-2-for-this-formula-see-3-halo-piperidine.gif\" alt=\"compound with 1 degree of unsaturation will return value of 2 for this formula see 3 halo piperidine\" width=\"600\" height=\"148\" \/><\/p>\n<p>Each successive degree of unsaturation will increase this number by 2. For instance, 2-chloropyridine C<sub>5<\/sub>H<sub>4<\/sub>NCl gives us 8:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15419\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/12-each-degree-of-unsaturation-reduces-this-number-by-2.gif\" alt=\"each degree of unsaturation reduces this number by 2\" width=\"600\" height=\"81\" \/><\/p>\n<p>Now 8 is not the degrees of unsaturation. It&#8217;s merely the number of hydrogens &#8220;missing&#8221; from the corresponding non-cyclic\u00a0alkane of the same carbon count.<\/p>\n<p>In order to make this equation give us the actual degrees of unsaturation, <strong>we need to divide everything by two<\/strong>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15420\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/13-final-modification-for-formula-with-degrees-of-unsaturation-is-equal-to-one-half-times-2-times-carbons-plus-2-plus-nitrogens-minus-hydrogens-minus-halogens.gif\" alt=\"final modification for formula with degrees of unsaturation is equal to one half times 2 times carbons plus 2 plus nitrogens minus hydrogens minus halogens\" width=\"630\" height=\"70\" \/><\/p>\n<p>We can really condense things by using the symbols H, C, N, and X to represent hydrogens, carbons, nitrogens and halogens, respectively.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15421\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/14-unified-formula-for-degrees-of-unsaturation-index-of-hydrogen-deficiency-including-carbon-nitrogen-hydrogen-halogens.gif\" alt=\"unified formula for degrees of unsaturation index of hydrogen deficiency including carbon nitrogen hydrogen halogens\" width=\"630\" height=\"131\" \/><\/p>\n<p>This is our final form for the equation for &#8220;degrees of unsaturation&#8221;, or &#8220;index of hydrogen deficiency&#8221; if you prefer.<\/p>\n<h2><a id=\"eleven\"><\/a>11. Applying The IHD Formula To Four Real-Life Examples<\/h2>\n<p>OK, now for those real-life examples I mentioned above.<\/p>\n<ul>\n<li>C<sub>9<\/sub>H<sub>8<\/sub>O<sub>4 \u00a0 \u00a0\u00a0<\/sub><\/li>\n<li><span title=\"Carbon\">C<sub>21<\/sub><span title=\"Hydrogen\">H<\/span><sub>30<\/sub><span title=\"Oxygen\">O<\/span><sub>2\u00a0<\/sub><\/span><\/li>\n<li><span title=\"Carbon\">C<\/span><sub>17<\/sub><span title=\"Hydrogen\">H<span style=\"font-size: small;\"><span style=\"line-height: 20px;\">21<\/span><\/span><\/span><span title=\"Nitrogen\">N<\/span><span title=\"Oxygen\">O<sub>4<\/sub>\u00a0<\/span><\/li>\n<li><span title=\"Carbon\">C<\/span><sub>11<\/sub><span title=\"Hydrogen\">H<\/span><sub>15<\/sub><span title=\"Nitrogen\">N<\/span><span title=\"Oxygen\">O<\/span><sub>2\u00a0<\/sub><\/li>\n<\/ul>\n<p>Let&#8217;s plug each of them into our formula. You should get:<\/p>\n<ul>\n<li>C<sub>9<\/sub>H<sub>8<\/sub>O<sub>4 \u00a0 \u00a0\u00a0<\/sub>[6 degrees of unsaturation]<\/li>\n<li><span title=\"Carbon\">C<sub>21<\/sub><span title=\"Hydrogen\">H<\/span><sub>30<\/sub><span title=\"Oxygen\">O<\/span><sub>2\u00a0<\/sub>[7 degrees of unsaturation]<\/span><\/li>\n<li><span title=\"Carbon\">C<\/span><sub>17<\/sub><span title=\"Hydrogen\">H<span style=\"font-size: small;\"><span style=\"line-height: 20px;\">21<\/span><\/span><\/span><span title=\"Nitrogen\">N<\/span><span title=\"Oxygen\">O<sub>4<\/sub>\u00a0[8 degrees of unsaturation]<\/span><\/li>\n<li><span title=\"Carbon\">C<\/span><sub>11<\/sub><span title=\"Hydrogen\">H<\/span><sub>15<\/sub><span title=\"Nitrogen\">N<\/span><span title=\"Oxygen\">O<\/span><sub>2\u00a0<\/sub>[5 degrees of unsaturation]<\/li>\n<\/ul>\n<p>Now, let&#8217;s look at each of the molecules. You&#8217;ll find that the calculated degrees of unsaturation agrees with the sum of [multiple bonds and rings] in the molecule.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-15422\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/12\/15-examples-of-index-of-hydrogen-deficiency-calculation-incorporating-aspirin-thc-cocaine-and-mdma-calculate-degrees-of-unsaturation.gif\" alt=\"examples of index of hydrogen deficiency calculation incorporating aspirin thc cocaine and mdma calculate degrees of unsaturation\" width=\"600\" height=\"877\" \/><\/p>\n<p>Super useful. Super easy.<\/p>\n<p>With the structure in front of you it seems obvious. But if you&#8217;re dealing with an unknown it can be very helpful, like we saw with deer tarsal gland hormone in the last post.<\/p>\n<p>In the next post, we&#8217;ll start delving into the mysteries of spectroscopy. We&#8217;ll start with one of the simplest spectroscopic techniques &#8211; <a href=\"https:\/\/www.masterorganicchemistry.com\/2016\/09\/16\/introduction-to-uv-vis-spectroscopy\/\">UV-Vis spectroscopy<\/a> &#8211; and show how it can be used to deliver clues about the structures of various molecules.<\/p>\n<hr \/>\n<h2>Notes<\/h2>\n<div class=\"related-articles\"><p><strong>Related Articles<\/strong><\/p><ul><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2016\/09\/08\/conjugation_and_color\/\" class=\"\"><span>Conjugation And Color (+ How Bleach Works)<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2016\/11\/23\/quick_analysis_of_ir_spectra\/\" class=\"\"><span>Infrared Spectroscopy: A Quick Primer On Interpreting Spectra<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2016\/08\/23\/structure-determination-case-study-deer-tarsal-gland-pheremone\/\" class=\"\"><span>Structure Determination Case Study: Deer Tarsal Gland Pheromone<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2016\/09\/16\/introduction-to-uv-vis-spectroscopy\/\" class=\"\"><span>Introduction To UV-Vis Spectroscopy<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2016\/09\/27\/uv-vis-spectroscopy-some-practice-questions\/\" class=\"\"><span>UV-Vis Spectroscopy: Practice Questions<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2013\/04\/02\/epoxidation-hydroxylation-cyclopropanation-alkene-mechanism\/\" class=\"\"><span>Alkene Addition Pattern #3: The \u201cConcerted\u201d Pathway<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2010\/10\/06\/functional-groups-organic-chemistry\/\" class=\"\"><span>Meet the (Most Important) Functional Groups<\/span><\/a><\/li><li><a href=\"https:\/\/www.masterorganicchemistry.com\/2014\/02\/18\/introduction-to-cycloalkanes-1\/\" class=\"\"><span>Introduction to Cycloalkanes (1)<\/span><\/a><\/li><\/ul><\/div>\n<h2><a id=\"quiz\"><\/a>Quiz Yourself!<\/h2>\n<p><br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2810-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><br \/>\n<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/2811-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the 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decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3231-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><br \/>\n<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3192-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><br \/>\n<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3193-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><br \/>\n<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3194-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><br \/>\n<br \/>\n<img loading=\"lazy\" decoding=\"async\" class=\"wp-image-36214 aligncenter\" src=\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/quiz-previews\/3195-Front-Image-Only.png\" alt=\"\" width=\"600\" height=\"450\" \/><\/a><\/p>\n<p style=\"text-align: center;\"><a href=\"https:\/\/www.masterorganicchemistry.com\/moc-membership\/\"><strong>Become a MOC member<\/strong><\/a> to see the clickable quiz with answers on the back.<\/p>\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Degrees of Unsaturation (Index Of Hydrogen Deficiency) The molecular formula of a compound can give clues about its structure. The formula for an alkane follows <\/p>\n","protected":false},"author":1,"featured_media":15407,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[386],"tags":[1115,1116,1114,1117],"post_folder":[],"class_list":["post-10102","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-spectroscopy-2","tag-degrees-of-unsaturation","tag-index-of-hydrogen-deficiency","tag-index-of-unsaturation","tag-molecular-formula"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Degrees of Unsaturation (or IHD, Index of Hydrogen Deficiency)<\/title>\n<meta name=\"description\" content=\"Degrees of unsaturation is easily calculated by using the IHD formula below. The IHD tells you how many double bonds \/ rings are present. 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