Draw the condensed structural or line-angle formula, if cyclic...

Question

Draw the condensed structural or line-angle formula, if cyclic, for each of the following:

d. 3-methylhexanal

Accepted Answer

Welcome everyone. Let's look at our next problem. It says draw the following de condensed structural formula or the line angle formula. If cyclic of three ethyl, five methyl Hexon out, we have four different answer choices with four different possible structures. Note all of these are condensed structural formulas. So we can assume our compound is not cyclical. We'll go into them in more detail as we work our way through the problem. So we have 53 ethyl, five methyl heany. So indeed, we don't see any prefix like cyclo, we don't see any benzene rings. So no cyclic compound. The A L ending means we have an aldehyde. So that needs to be on a terminal carbon. It's part of the main chain which is hex L. So we have a six carbon chain and since there's no number in front of the hex, now we'll assume the aldehyde is on carbon one, which makes sense that it has to be the terminal carbon. So we'll draw out six carbons, put a little space after each one to fill in hydrogens where necessary 456 with lines between them for bonds. Since we're drawing condensed structural formula. Now, our aldehyde will be on our carbon one. So let's give the first carbon a double bond to an oxygen and then a hydrogen. So we have our six, in terms of our numbering system, we know that, that aldehyde carbon must be carbon one. So we'll just go through and add numbers to each of these 456. I've done the numbers in red just to avoid it getting a little confusing with any branches or things. So we've got our six carbons, our aldehyde group, let's look at our substituents. So we have three ethyl. So an ethyl group on carbon three. So we'll draw a line up from carbon three and write in C two, C three and then five methyl. So a methyl group on carbon five. So line up from that and write in ch three. Now we just fill in hydrogens where needed. So carbon one has four bonds. It already has the hydrogen, the double bond to the oxygen and a bond to carbon two. No hydrogen is needed there. Carbon two is an internal carbon with no substituents. So we fill in H two, carbon three has three bonds. So we need one hydrogen. Carbon four, no substituents. So H two, carbon five has a branch. So three bonds. So it just needs one hydrogen and then carbon six is terminal with no substituents. So three hydrogens. So we have HC with a double bond to an och two ch with a ethyl group CH two CH three, then ch two ch with a methyl group CH three and then finally CH three. So we have our structure, let's see which of these is correct. So when we look at choice A, we see there's our aldehyde on carbon one, CH two, ch, here's carbon three with the ethyl group, carbon four, carbon five, but carbon five has a second ethyl group instead of a methyl group. So that's why choice A is incorrect. When we look at Choice B, we see we have our aldehyde on carbon one and we go 23, there's our ethyl group on carbon three. Carbon four, carbon five has a methyl group and NCH three. So we've got six carbons are aldehyde ethyl and methyl groups in the right place. So it looks like choice B is our answer. We'll be thorough here and keep going. When we look at Choice C, we've got our aldehyde and carbon one. But then there's only one substituent, an ethyl group on carbon five. So we're missing our, so we'll say no methyl group and the ethyl groups in the wrong place as well. So ethel wrong place. So choice C definitely incorrect and then choice D has no branches at all. So no branches. So it is definitely wrong. So we can rule out choice D and in fact, if we were on a test and wanted to go a little bit faster, we could have given these a quick look. And just from the name right away said, oh choice A no methyl choice D no branches. So if we were on a test and really trying to be efficient, rather than drawing out your structure first, it's a good idea. In that case, we could have ruled out three choices right away and gotten to our answer without even drawing that structure. So just keep that in mind with a multiple choice question. So our answer here for the correct condensed structural formula is choice B see you in the next video.

Draw the condensed structural or line-angle formula, if cyclic, for each of the following:
d. 3-methylhexanal

Key Concepts

Condensed Structural Formula

Line-Angle Formula

Cyclic Compounds

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