Draw a condensed structure for each of the following:
i....

Question

Draw a condensed structure for each of the following:

i. diethylacetylene

j. di-tert-butylacetylene

Accepted Answer

Hi, everyone. Let's take a look at the next problem. It says, give the correct condensed structure of the following compounds. And then we'll have two compounds where we're given their Iupac name. So we'll go back to those in a second. But first, let's remember what we're looking for when we're drawing a condensed structure. That's a structure where all of the atoms will be shown as their symbols, but no bonds will be indicated. And, and parentheses will be used to indicate substituent branches or groups of ch sub units with subscripts outside those parentheses to indicate a number of these things. And you'll be writing essentially all of this on a single line. So that's why it's condensed, none of the arrangements in space. Um with the exception of rings because cyclic rings can't be indicated in this fashion. So if you get one of those, you will have to show some bonds there in the ring itself. So with that in mind, let's look at each of our molecules. Now, just going from an Iupac name to a condensed structure is pretty difficult because you want to be able to get kind of a visual representation of the way the substituents are coming off in branches to help you in arranging that condensed structure. So you can draw sort of a modified condensed structure where you show the bonds, maybe use, use space to show if something's coming off to one side or not. I prefer actually to draw a skeletal structure. It's quick and easy and it shows you everything's orientation and space. So we'll start with compound number one. So the name we're given is 25 dimethyl hex three im. So let's start with our basic chain. It's hex line. So it's six carbons and it's hex three iron. So there's a triple bond from carbon three to carbon four. So let's go ahead and draw that sort of base chain. So we'll drop 123, there's carbon three. Now, triple bonds are a little tricky since they have that linear geometry. So I like to put a dot There for carbon three and then four and then 52345 will all be in line there. So add the triple mond from C three to C four and then we have six Carmens total. So there's five and then six makes this funny little zigzag here and then we're told. So we've got our main chain hex three iron and then we have 25 dimethyl. So carbon two as a methyl group and carbon five is a methyl group. So now we write it as a condensed structure well, you could draw, you could write CH three and then C oops, excuse me, ch three and then CH two. And then in parentheses, CH three to show that methyl group substituent coming off of carbon two, but kind of a, a nicer way to write it and give sort of a little bit of a better picture when you look at the immense structure of what it looks like the way since we have that metal group. Um In each case, on the second to last carbon, you can write it as two methyl groups. So you can say there's CH three in parentheses and then put a two subscript showing two methyl groups at the end there. So you've got two methyl groups, they're both attached to the CH two. So after the premises and subscript, write CH two, excuse me, not CH two, it gets a little tricky sometimes remember that this carbon has three bonds, there's only a single hydrogen. So always double check that you are writing the correct number of hydrogens for your carbons. Now, we go to carbon three and carbon four, they're in a triple bond. They each have a substituent. So they have zero hydrogens. So we actually will just have cc next to each other, then it's symmetrical. So we have the same thing on the other side. So here's ach and then two methyl groups. So ch three in parentheses again. And in subscript two, so you can see how structuring it this way. Um phrasing the structure as two methyl groups at the end instead of showing carbon one and then carbon two with a branch kind of gives you a better overall picture of the way the molecule is structured when you look at the condensed structure, but either way is correct as a description. So there's our condensed structure for molecule number one. Again, that's CH three in parentheses, subscript two CHCCCH and then CH three in parentheses, subscript two. So now let's look at molecule number two. So this is 36, diethyl oct four iron. So again, we've got a, an alky here with a triple bond or we have an oc time. So we have eight carbons in the chain and our triple bond is from C four to C five and then two hyl groups on carbon three and six. So we'll do our main chain here. We've got eight carbons. So we do it in that zigzag form for the skeletal structure. 12, 34. So here's carbon four. Put a little dot there to keep it straight with a triple bond to carbon five. And then in a straight line from that, there's Carmen six. So 3456, all in a straight line and then Carmen seven and Carmen eight. So there's our triple bond in place. Now, we just need to indicate we've got ethyl groups on carbon three and Carmen six. So here is our ethel group on carbon three ethyl group on carbon six. And actually, I've run out of space here. I need to move where I wrote C four triple bond to C five because I, I'm going to run into my ethyl branch there. So there we go. So now we're going to have the same thing here where we could write the H three CH, two ch and then the ethyl group in parentheses. But again, if we look at the shape of this molecule and the symmetrical shape of it, we have this triple bond in the middle and we essentially on carbon three and carbon six have two ethyl branches. One's a substituent and one's the end of the chain. But again, writing the structure as two ethyl branches gives us a better picture. So we can write our condensed structure as parentheses, CH three CH two. So that's an ethyl branch, close parenthesis, subscript 22 ethyl branches. Now we're on to carbon three which is CH, now we're to our triple bond. So just cc no hydrogens, then ch again and then in parentheses, ch in this case, I would write CH two CH three because we want to show the order of the atoms here and the CH two groups will be coming first as we go from left to right and then subscript two. So you can see there again, we have the two ethyl groups as a group and then the middle part and the two ethyl groups is a group at the end. So notice we don't indicate bonds here. So we don't specifically indicate there's a double bond or triple bond. But a key right away whenever you see two carbons just by themselves like that, no hydrogens around no substituent groups, that's a key that you've got a triple bond there. So one way to kind of spot that when looking at a condensed structure. So that's our construction for number two in parenthesis, CH three CH two, subscript two, CHCCCH then parenthesis CH two CH three and then subscript two. See you in the next video.

Draw a condensed structure for each of the following:
i. diethylacetylene
j. di-tert-butylacetylene

Key Concepts

Condensed Structural Formula

Alkynes

Tertiary Alkyl Groups

Watch next