00:02
Hi there.
00:03
In this question, we need to determine the number of hydrogens that should be placed on each of the indicated locations.
00:12
Well, to do this, we need to know a couple of things.
00:14
One is that carbon is typically going to make a total of four bonds.
00:24
So any remaining bonds that are not shown are going to be to hydrogens.
00:29
Nitrogen makes a total of three bonds to other atoms.
00:39
And oxygen, typically makes a total of two bonds.
00:47
So using this information, we can determine each of these.
00:51
All right.
00:52
So i am going to go from left to right here, and i'm just going to look at each indicated carbon, or nitrogen, or oxygen, whatever the arrow is pointing at.
01:04
So the first one is pointing to a carbon that is part of a ring.
01:08
It's double bonded to a carbon.
01:10
It's single bonded to a carbon.
01:12
So that takes three bonds.
01:15
That means that fourth bond must be to a hydrogen.
01:19
So the first box on the left, the answer should be just one hydrogen.
01:27
All right.
01:28
For the next one going across, we see a carbon that is bonded to a carbon in a ring, bonded to another carbon in a ring, bonded to another carbon in a ring, and then bonded to an oxygen.
01:47
That is, of course, then bonded, that's bonded to a hydrogen.
01:49
But this carbon itself already has four bonds.
01:54
Therefore, it's going to have zero hydrogen atoms attached to it.
02:05
All right.
02:05
The next one go in across.
02:08
We see that we have carbon.
02:09
That's part of a ring.
02:10
It's single bonded to two other carbons.
02:13
That means it has two bonds available...