1. What structures for myrcene are consistent with the facts?
2. Based on the isoprene rule (naturally occurring terpenes are made up of isoprene segments) what is the most likely structure for myrcene?
Dihydromyrcene C10H18, formed from myrcene absorbs 2 moles of hydrogen to form C10H22. Upon cleavage with KMnO4, dihydromyrcene yields the structures showin in .jpg #2 (I5Q2b):
3. Keeping in mind the isoprene rule what is the most likely structure for dihydromyrcene?
4. Is it surprising that a compound of this structure is formed by reduction of myrcene? Explain.
Part of your difficulty may have come from the fact that your initial statement is not exactly true. You wrote: "Myrcene, C10H16, a terpene, absorbs three moles of hydrogen to form C10H22. Upon ozonolysis myrcene yields the two compounds shown in the first attached .jpg (I5Q2a)."
However, there are three structures shown in the jpg file. Now, how do we get a 10 carbon myrcene from three products that add up to only 9 carbons? Clearly, there must be 2 moles formed of the one-carbon product. Therefore, the products of myrcene ozonolysis are 2 moles of formaldehyde (H2C=O), 1 mole of acetone (CH3C=OCH3) and 1 mol of the other compound which is C5H6O3.
Now, that we know that, we must figure out how they go together. It's not that difficult. Everywhere there is a carbonyl group (C=O) in the products formed, there was a carbon-carbon double bond (C=C) in myrcene. Since we see the C5H6O3 product with 3 carbonyl groups, we ...
This solution addresses two questions about ozonolysis of mycene and the isoprene rule.