Naming Alkanes with Substituents - Video Tutorials & Practice Problems
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concept
Rules for Naming Alkanes with Substituents
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54s
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So when it comes to native Organic Compounds, the name consists of a parent chain, the name of substituents and their locations, and a substituent. Now, substituent, we're gonna say is an alkyl group that branches off the parent chain. For this portion of naming, we're gonna say the name format is the location of our substituent, and then ending with the parent name. Alright. So as we do more and more of these, the name format's gonna become second nature to everyone. So, just pay attention, and take care because there are steps involved, a process. Remembering the process is the easiest way to name any organic compound you come face to face with.
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example
Naming Alkanes with Substituents Example
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5m
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Here it says, give the systematic name of the following alkane. Right. So to name this, we're gonna have to follow the given steps. So, step 1, we find the longest carbon chain, which is the parent chain, and assign name according to the prefixes. Now, if a tie between longest chain, choose the chain with more substituents. Now, when it comes to finding the longest carbon chain, you have to let go of the fact that we're reading from left to right. When it comes to looking at an organic molecule, you may look left to right may give you the longest chain, or right to left, or top to bottom, or bottom to top. You have to be able to look in all directions. So if we take a look here, what's the longest possible chain? Let's see. 1, 2, 3, 4. Okay. 1, 2, 3, 4, 5, 6, 7. 1, 2, 3, 4, 5, 6, 7. So it looks like there's 2 ways that give me 7. And regardless of which way you go, if we went this way, we'd have 2 substituents. This one branching off and this one branching off. If we went the other way, it'd be the same thing. Where going this way, we'd have these 2 s substituents. Alright. So our longest carbon chain is 7 carbons long. Now, step 2, assign names to all substituents, and this is important. Step 3. Start numbering the chain from the closest substituent. If a tie between substituents, compare the next closest substituent. If still a tie, number in alphabetical order. Alright. So if we go down here, I've highlighted what we were just talking about. The longest carbon chain I decided to highlight it this way. This gives me a 7 carbon chain as the parent chain. And what's highlighted in orange are our substituents. So here we go 123, we get to this substituent, We go 123, we get to this substituent. It's tied. Counting the carbon 3 from either side gets us to a substituent. But if we identify these, this is 1 carbon, so this would be a methyl group. This is 2 carbons, so this is an ethyl group. We said, if still a tie, distance from the ends to the first substituent, number in alphabetical order. E comes before m, which means we're gonna number it this way, 123, and then 4, 5, 6, 7. Now, step 4, you're going to assign numbers, which gives us the location for each substituent. When more than 1 identical substituents use the numerical prefixes of di for 2, tri for 3, and tetra for 4. Alright. So we have on carbon number 3, ethyl. So this we're gonna say, we're gonna use 3 ethyl. Okay. Name substituents in alphabetical order. Prefixes do not count, use commas to separate numbers from numbers, and we're gonna use dashes to separate letters from numbers. Letters are not separated from letters. So a lot is being said here, so let's work this out. We're gonna name the substituents alphabetically, and we're gonna give their number locations. So ethyl is on carbon number 3, so that's 3. And remember, we're gonna use dashes to separate letters from numbers, so 3 dash ethyl. Methyl's on carbon number 5, dash 5 methyl, and then we have a 7 carbon chain. 7 carbons is hept, and it's an alkane, so it's heptane. So this would be the name of this alkyl group, or this alkane molecule. 3 Ethyl-5 Methyl-heptane. This would be our final answer. Again, it gets a little bit jarring in terms of naming these types of molecules, but with enough practice it becomes second nature. So keep at it, and you'll get to master naming all these different types of organic compounds.
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Problem
Problem
Provide a systematic name for the molecule.
A
7-isopropyl-2,3-dimethyldecane
B
2,7,8-trimethyl-3-propylnonane
C
4-isopropyl-8,9-dimethyldecane
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2,3,8-trimethyl-7-propylnonane
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Problem
Problem
Draw a structure for 2,6-dimethyl-4-propylnonane.
A
B
C
D
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Problem
Problem
Draw a structure for 4-tert-butyl-3-isopropyl-2-methyloctane.