Constitutional isomers of C4H10 | Alkanes – Dr K
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Constitutional isomers of C4H10 | Alkanes – Dr K


The question is asking to draw out all
constitutional isomers for C4H10. Since this chemical formula fits in the
general formula of CnH2n+2, that means it’s an alkane. Let’s start by drawing a four carbon chain, four carbons connected straight in a row like this. We know that carbon can make four bonds, and since the first carbon is already
connected to one carbon, that means it, will connect to three hydrogens. The second carbon is already connected to two carbons on the left and right so that means it has a remaining of four minus two equals two bonds. The third carbon is the same as the second carbon, so it will also have two bonds. The last carbon only connected to one carbon like our first carbon, so therefore four minus one equals three bonds. Now we put in all the hydrogen’s and we have our first structure of C4H10. Since there’s no other way to draw four carbon chain, our next isomer will be three carbon long. Place in the remaining carbon on
the second carbon like this. Now what if we place the remaining carbon at the end like this. Is this another isomer? But actually it’s
not. We’ve already drawn this guy. Look, it has four carbon connected straight in a row, so back to our three carbon chain. Let’s fill in the rest of the bonds. The
first carbon is connected to only one carbon, so it has three bonds. The second carbon is already connected to three other carbons, so only left one bond. Third one is the same as the first one, so three bonds, and this substituent, the
guy, the carbon hanging there, it’s also connected to one carbon so that means it
has three remaining bonds as well. Now we fill in with hydrogen’s and we have our second and final structure for C4H10. These are the two isomers we’ve drawn
for C4H10. Well, we can’t draw any more isomers for C4H10 because if we were to
start with two carbon chain like this and then we have two extra carbons, right?
So, if I place one carbon on each of the carbons like this, in reality it is the
same as our first isomer because you can count four carbons straight in a row
like this. Also, if we were to start with two carbon chain and then we place
the remaining carbons on the first carbon, it’s actually it’s the same as
our second isomer because we actually have a three carbon chain with one
carbon substituent on carbon number two. I hope you find the video helpful. Do subscribe. Thanks for watching and I’ll see you in the next video.

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