[4gkenzy]

So for this one, I understand that the reaction type will be catalytic hydrogenation. I know that Pd/C is the catalyst in this instance. So, I know that a double bond will be broken and replaced with hydrogens. However, I am having trouble knowing which ones will be replaced.

Here is my prof's answer:


So, how was I supposed to know it was the carbons here:



that are being hydronized and not the ones across from it? Just confused in general here. Also don't even know where to begin with determining the degrees of unsaturation.

My answer looked something like this:



Ignore the blue.

Why would that be wrong?

[spirochete]

Your answer is correct. Your confusion indicates that you aren't thinking about all the invisible hydrogens. If you make these mistakes frequently, you might want to read first chapter of "organic chemistry as a second language" by Klein. It's easy to find on the internet, or it's fairly cheap to buy a used copy.

[Babcock_Hall]

Being able to calculate the number of degrees of unsaturation (the hydrogen deficiency index) is a useful skill, especially for problems involving unknowns.  It compares the maximum possible number of hydrogens that a given number of carbons could hold, with how many hydrogens are actually present.  You can ignore oxygen atoms in this calculation.  The final result tells you about the numbers of double bonds, triple bonds, or rings that are present.