If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:2:57

Video transcript

think we're ready now to tackle some more or even more complicated example so let's draw something crazy here so let me draw a chain let me draw it like that and so like we've done in all of the examples you want to find the longest chain we could count from here one two three four five six seven eight or maybe it's one two three four five six seven no or maybe it's one two three four five six seven eight nine ten that is our longest chain let me just let me make that in green so our longest chain here is in green so this decade this sorry this backbone has ten carbons in it the prefix for 10 is Dec it is a alkane since it has all single bonds so we can write decane for the backbone and then it has a group right here it has a group right here and this group consists of 1 2 carbons attached to the backbone the prefix for 2 carbons is F so this is an ethyl group the yl is because it's a group attached to the main alkane chain so we call this ethyl ethyl decane but we have to specify where the ethyl group is attached and we want to give it as low of a number as possible so we start counting on the side closest to it so it's 1 2 3 4 5 so this is 5 ethyl decade now let's complicate this a little bit more so let me just copy and paste this copy and then paste so I have pasted it there and let me complicate this molecule a little bit more let me add another ethyl group to it let me add another ethyl group to it so let's say it is we have another ethyl group over there now what is this going to be well we still the longest chain is still going to be that thing in green so it's still going to be a decane it's still going to be a decane but now we have two ethyl groups one on the five carbon one two three four five and then one on the six carbon and then one on the six carbon so what we write here is you might be tempted to write five Ethel six Ethel decane which really wouldn't be wrong but it would just be maybe more letters and you want to write instead you're right instead you write five comma six die Ethel die die Ethel die Ethel decane the five six tells us the two carbons on the main backbone that the ethyl groups are attached to and the die says that we have two ethane or two ethyl groups I should say not ethene groups two ethyl groups one over here and one right over here