Α-Terpinene, C10 H16, is a pleasant-smelling hydrocarbon...

$\alpha$ -Terpinene, $\mathrm{C}_{10} \mathrm{H}_{16},$ is a pleasant-smelling hydrocarbon that has been isolated from oil of marjoram. On hydrogenation over a palladium catalyst, $\alpha$ -terpinene reacts with 2 molar equivalents of $\mathrm{H}_{2}$ to yield a hydrocarbon, $\mathrm{C}_{10} \mathrm{H}_{20} .$ On ozonolysis, followed by reduction with zinc and acetic acid, $\alpha$ -terpinene yields two products, glyoxal and 6 -methyl- 2,5 -heptanedione. (a) How many degrees of unsaturation does $\alpha$ -terpinene have? (b) How many double bonds and how many rings does it have? (c) Propose a structure for $\alpha$ -terpinene.

$\alpha$ -Terpinene, $\mathrm{C}_{10} \mathrm{H}_{16},$ is a pleasant-smelling hydrocarbon that has been isolated from oil of marjoram. On hydrogenation over a palladium catalyst, $\alpha$ -terpinene reacts with 2 molar equivalents of $\mathrm{H}_{2}$ to yield a hydrocarbon, $\mathrm{C}_{10} \mathrm{H}_{20} .$ On ozonolysis, followed by reduction with zinc and acetic acid, $\alpha$ -terpinene yields two products, glyoxal and 6 -methyl- 2,5 -heptanedione.
(a) How many degrees of unsaturation does $\alpha$ -terpinene have?
(b) How many double bonds and how many rings does it have?
(c) Propose a structure for $\alpha$ -terpinene.

Key Concepts

Degrees of Unsaturation

This concept refers to the number of rings and/or multiple bonds present in a molecule based on its molecular formula. It is calculated using the formula (2C + 2 ? H)/2 (adjustments are made for heteroatoms), and it provides insight into the overall level of unsaturation, which is instrumental in deducing structural features of organic compounds.

Hydrogenation Reaction

Hydrogenation is a chemical reaction that adds hydrogen atoms to unsaturated compounds, usually in the presence of a metal catalyst such as palladium. In organic synthesis, it is used to convert carbon–carbon double bonds into single bonds, thus reducing the degree of unsaturation, which can be quantitatively analyzed to determine the number of double bonds initially present.

Ozonolysis Reaction

Ozonolysis is a reaction where ozone cleaves carbon–carbon double bonds to form carbonyl-containing compounds (aldehydes and/or ketones) upon workup with reducing agents. This reaction is valuable in structural elucidation because the pattern of cleavage and the resulting products can reveal the connectivity and placement of double bonds within the original molecule.

Structure Elucidation

Structure elucidation involves using a combination of chemical reactions and analytical methods to determine the molecular structure of an organic compound. By analyzing how a compound reacts, for example through hydrogenation and ozonolysis, chemists can infer the number and type of unsaturated sites (double bonds, rings) and propose a plausible structural framework that is consistent with the observed reaction products.

Transcript

00:03 Question number 56 is alpha terpenine so in such kind of questions actually while reading you have to make the flow diagram then the things will be more clear so first it is alpha turpinine that means p -i -n -e turpinine it is c -10 h -60 is a pleasant story smelling hydrocarbon that has been isolated from oil of marjoram.

00:48 This is given.

00:50 On hydrogenation.

00:53 Hydrogenation, that means reaction with hydrogen.

01:00 On hydrogenation over a palladium catalyst, you can write here.

01:08 Catalyst alpha turpinine reacts with two molar equivalents of hydrogen.

01:14 That means here you are taking two moles.

01:22 Of hydrogen.

01:25 To yield a hydrocarbon, you are getting a hydrocarbon and this hydrocarbon is c10 h20.

01:48 It is again given on ozonalysis followed by reduction on ozonalysis.

01:59 That means the first step is ozonellysis, reaction with ozone.

02:03 And second step is reduction reduction with zinc and acetic acid zinc and acetic acid so it is acetic acid is taken for the ozone after ozonolysis alpha turtinent yields two products glyoxyl one is glyoxal glioxal is the compound that is c single bond c having this two double bond here with oxygen and one hydrogen.

03:00 This compound is glyoxyl.

03:04 And second compound is given that is 6 methyl 25 haptophthyne.

03:15 That means the structure of this compound should be ch3.

03:19 Ch3 c double bond o, ch2, one more ch2, then one carbon with the double bond o and one ch must be here that is further attest to methyl group and here also it methyl group must be present.

03:56 So this compound is 6 methyl, this 6 methyl, 25, 25, haptane, diome.

04:09 So this is the compound which is already given in the question.

04:14 Now the question starts...

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