Constitutional isomers of C5H10O | Aldehyde & Ketone – Dr K
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Constitutional isomers of C5H10O | Aldehyde & Ketone – Dr K

August 25, 2019

We’re gonna draw out all possible
aldehyde and ketone isomers for C5H10O in this video. Have you tried out on your own? Well, stay tuned until the end of this video to compare notes. Let’s begin. Quick recap. Aldehyde has a carbonyl functional group which is C double bond O connected right next to a hydrogen.
Note that this CHO group is always at the first carbon for aldehyde,
whereas for ketone, it has the same carbonyl group but it’s next to two
carbons so there’s no hydrogen connected right next to the carbonyl group. That’s
the difference between aldehyde ane ketone. Let’s start with aldehyde. Since we have five carbons, let’s place the CHO group at the beginning and then we’ll
add in the remaining carbons in a row like this. That’s our first aldehyde
isomer and that has five carbon chain because we have five carbon straight in
a row. Now instead of placing all five carbons in a row we can place four in a
row. The fifth carbon is stuck on carbon 2.
Now let’s keep the same framework of four carbon chain and then we’ll see if
we can stick the fifth carbon elsewhere. In fact we can place it on carbon 3. This
is different from the previous aldehyde, so, that gives us our third aldehyde and
we are now done with 4 carbon chain because if we were to stick the fifth
carbon on carbon 4 it will give us a five carbon chain which is the same as
our first structure. Now, let’s see what we can do with a three carbon chain
aldehyde. We’ve used 3 carbon and one oxygen so that means we have two carbon left, so, let’s stick the two carbons on carbon 2. That will give us yet another
isomer. Now similar to previous example, we don’t want to stick anything at the
end of the carbon chain otherwise it will give us a repeat of what we have
already drawn. Since we can’t shorten the chain to 2 carbon that means we are done
with aldehyde. We fill out with the appropriate number of hydrogens and
that will give us these structures. Keep in mind that each carbon makes four bonds and be sure to check that each structure has 10 hydrogens. No more and
no less. Quick recap on how we drew all four isomers for aldehyde. We started
with longest chain which is a five carbon
chain and then we move on to the four carbon chain. We stick the remaining
carbon on C2 and then we draw another structure and place the remaining carbon
on C3. Once we’ve exhausted the four carbon chain we then shorten the chain
photo to three carbon chain and then we stick the remaining two carbons on C2
since we can’t shorten the chain anymore. We know that we have already drawn our
all isomers for aldehyde and we did it in a very systematic way. This increases
our probability for drawing all isomers correctly and with zero errors. Now let’s
move on to ketone. Let’s start by placing the carbonyl
group sandwiched by two carbons. Since we’re dealing with five carbons, let’s
place the remaining two carbon straight in a row like this and that will give us
a five carbon chain ketone with carbonyl group at C2. Let’s keep working with this
five carbon chain and now we will move the carbonyl group to C3. That will give
us another isomer. If we were to move the carbonyl group to carbon 4 it will
actually be the same as the first structure, so, let’s move on to the 4
carbon chain now. Here’s our 4 carbon chain and then we will stick the fifth
carbon on C3. Looks like there’s only one way to stick the fifth carbon on the 4
carbon chain. If we were to stick the fifth carbon on C4. It will actually give
us the same structure as the first ketone. Also, we can shorten the chain to
three carbon chain so that means we’re actually done drawing all ketones.
Let’s fill up the structure with remaining hydrogens and here’s what we
got. Here are our three ketones. To recap, we have a total of four aldehydes and
three ketones for C5H10O. If you’re interested in drawing other isomers
aside from aldehyde and ketone for C5H10O, let me know in the comments and
I’ll post a video for it. I hope you find the video helpful. Do subscribe and thanks for watching.

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  1. Thanks a lot for explanation. I was facing a bit problem in it . Now the doudts r solved thanks again!

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