Organic Chemistry Naming Examples 3 Organic Chemistry Naming Examples 3
Organic Chemistry Naming Examples 3
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- We've got a few more molecular structures to name, so let's
- look at this first one right here.
- The first thing you always want to do is identify the
- longest chain.
- If we start over here, we have one, two, three, four, five,
- six, seven, eight, nine, ten, eleven, twelve, thirteen
- carbons, looks pretty long.
- Now what if we start over here?
- This looks like it could also be a long chain: one, two,
- three, four, five, six, seven, eight, nine, ten, eleven,
- twelve, thirteen.
- So we have two different chains, depending on whether
- we want to go up here or whether we go over here, that
- have a length of thirteen.
- So you're probably asking, which chain do you choose?
- You should always, if we have two chains of equal lengths
- and they're the longest chains, you pick the one that
- will have more branches or more alkyl groups on it.
- So this group right here, if we pick this from here to here
- as our chain, we only have one group on it,
- that group up there.
- If we pick this chain, starting over here and then
- going over here, we have two groups on it.
- We would have this group over here and then we would have
- this group over here.
- This is the better chain to use because it has
- more groups on it.
- It has more groups, but the groups
- are smaller and simpler.
- So let's start counting.
- And the direction we want to count, we always want to start
- on the side of the chain where we're going to encounter
- something first, and everything is closer this end
- of the chain so we'll start counting here.
- One, two, three, four, five, six, seven, eight, nine, ten,
- eleven, twelve, thirteen, so we have thirteen carbons on
- our main chain.
- Let me draw our main chain.
- So our main chain is this thing in orange I'm drawing
- right here.
- That is our main chain.
- Thirteen, that's three and ten.
- The prefix is tridec- and it's tridecane because we have all
- single bonds here, so it's tridecane.
- Tridecane is the main chain.
- Then we have two groups over here.
- This one in green, this only has one the carbon branching
- off of the main chain, so it's prefix will be meth- and it'll
- be a methyl group, so that is methyl.
- That is a methyl group right there.
- Then this one down here, we have one, two, three carbons.
- the prefix is prop-, so this is a propyl group.
- And the methyl is sitting on the three carbon of our main
- chain and the propyl group is sitting on the four carbon:
- one, two, three, four.
- Now when we figure out what order to list them in when we
- actually write out the name, M, we just do it in
- alphabetical order.
- M comes before P, so we write 3-methyl before 4-propyl.
- The entire compound here is or the entire molecule is
- 3-methyl-4-propyltridecane And this is actually all going to
- be one word.
- You use dashes to separate when you have numbers, but if
- you have a word followed by a word, it just becomes
- propyltridecane, so 3-methyl-4-propyltridecane.
- And we're done.
- Let's do this one down here.
- Now this one seems a little bit more complex.
- The first thing to see is what is the largest chain or
- the largest ring that we have in our structure?
- The two candidates, we have this chain over here.
- This has one, two, three, four,
- five, six, seven carbons.
- Let's see how many carbons our ring has.
- Our ring has one, two, three, four, five, six, seven, eight,
- nine carbons.
- So the ring is the largest core structure in this
- molecule, so that will be our core structure.
- We have nine carbons-- let me highlight it-- so the ring is
- this right here.
- It has nine carbons.
- The prefix for nine is non-.
- It's all single bonds, so it's nonane, and it is in a cycle.
- It's a ring, so it's cyclononane.
- This part right here, that part right there, is
- We have several things that branch off of the cyclononane,
- so let's look at them one at a time, and then we'll think
- about how we're going to number them on the ring.
- We looked already at this at this chain that has seven
- carbons: one, two, three, four, five, six, seven.
- So that is a heptyl group.
- This over here, let's see what we're dealing with.
- We have one, two, three carbons, so that is just a
- standard propyl group.
- Then here, we have one, two, three, four carbons, so we
- could say this is a butyl group.
- But this isn't just any butyl group.
- If we use the common naming, the carbon we immediately
- touch on or that we immediately get to when we go
- off of our main ring, that branches off into three other
- carbons, so this is tert-, tert- for three.
- The tert- is usually written in italics.
- It's hard to differentiate that when you see it.
- I'll write it in cursive.
- This is tert.
- This is a tertbutyl group.
- Now, the next question is how do we specify where these
- different groups sit on this main ring?
- If you just had one group, you wouldn't have to specify it,
- but when you have more than one, what you actually do is
- you figure out which one would be alphabetically first, and
- that would be number one.
- Now, we have an H in heptyl, a P in propyl, and tert-butyl,
- you might say, well, do I use the T or do I use the B?
- And this is just the convention, you use the B.
- If you have sec-butyl or tert-butyl, you ignore the
- sec- or the tert-.
- If this was an isobutyl or an isopropyl, you actually would
- use the I, so it's a little bit-- I guess the best way to
- think about it is there's a dash here so you can kind of
- ignore it, but if this was isobutyl it would all be one
- word, so you would consider the I.
- So in this situation, we would consider the B, and B comes
- before P or an H, so that is where we will
- start numbering one.
- Then to figure out which direction to keep numbering
- in, we just go in the direction where we're likely
- to encounter the first or where we will encounter the
- first side chain, so we'll go in this direction because we
- get right to the propyl group.
- One, two, three, four, five, six, seven, eight, nine.
- So this compound, we're going to start with the
- alphabetically first side chain, so it's 1-tert-butyl.
- I'll write this in cursive.
- Then the next one alphabetically
- is the heptyl group.
- That's H for heptyl, so then it is 5-heptyl.
- And then we have the propyl, and then it is 2-propyl, and
- then finally cyclononane, and we're done!
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