Learn about Organic Chemistry 2, in this comprehensive video by bannanaiscool.
Read the full transcript »
Rob Lederer: So aliphatics are straight chained molecules. There are some of these organic molecules that have a raised structure and we'll talk about those later. So straight chains are aliphatics, they can have single bonds, double bonds and triple bonds though. The single bonded ones are called alkanes. So, now we are going to figure out how to name these, right? What's the nomenclature of these molecules? Nomenclature, like from the German Nomen and clature, which is I have no idea. How do we name alkanes? Well, first of all look, we are not going to be able to get anywhere until you memorize some prefixes in this system of naming. So, here is what they are and you got to get them under control then you can't go into a test or something like this and not have these because that's it you are done. You can have everything else, but if you mess up on any of these prefixes, you got to mess up in this entire unit of study. So, get this right the first time. Get -- it's a first time. Meth, eth, prop, but those are the four that are kind of new in terms of prefixes. The rest of them you have seen before when we named hydrates and ionic compounds and when we named molecules. But these four are different. Instead of mono, di, tri and tetra here are the four we use in organic chemistry. You can then calculate for this. Meth, eth, prop, bute; one, two, three, four; meth, eth, prop, bute; one, two, three, four get this right, get this now, and you are going to be okay. Meth one, eth two, prop three, bute four. Meth, eth, prop, bute. One two three four. Once you get that penta, hexa, hepta, octa, nano, deca you have seen that before. So, five six, seven, eight, nine, ten; 11 is one deca, 12 is dodeca 13 is triscdeca like as in trisdecaphobia, which is the fear of the number 13. There you go. You learn something other than chemistry. Now, I'll draw some molecules on the board and let's practice. So, let's start the nomenclature, okay. Now, here is the first in the series of the alkanes. One carbon long, so its meth. Write there. I didn't draw the hydrogens in because that's boring. So, CH4 meth means one carbon and all alkanes end in ane, and so therefore this is methane. There you go, no problem. Pretty simple. Alright, now how about this one right here? General formula CnH2n+2 two carbons one, two, three, four hydrogens plus two more six C2H6 that's the formula. So what do you call this right here? Single bond in between means it's an ane and there is two carbons that's eth, ethane. Simple as that, that's where we get all of this naming from. Now you look at this one, which is that condensed structural formula CH3 CH2 CH3 you say I'm not sure if that single bonds or double bonds or what? Well that you take one of these and you try it out. So, you can tell. See, you go one, two, three carbons long and three H is on this one two H is on that one, three H is on that one, you'll notice then that every carbon has four bonds, which loose diagram wise and formal charge wise is absolutely preferable. So all you going to get the carbon those four bonds and so therefore, right there CH3CH2CH3 three carbon chain, single bonds are all the way across that's going to be prop for three carbons and ane, propane. That's nothing to this. Okay, chemguy. I'm on a role, keep it coming. So one, two, three, four carbons long that's bute and single bonds all the way across that's butane. Right? Now, you know what? Here is the thing. It's not that anybody tries to be tricky or anything, but what if you take that carbon there and you put it right here, the longest continuous chain of carbons is one, two, three, four, and so that's still butane. This is an arm. What's this? It's still an arm. So, the point is whether its bent or its straight as long as its continuous that is how you count the chains to be able to get that number carbons and therefore to determine the name of it. Now, as opposed to this one, now take a look. One, two, three, four carbons.
Copyright © 2005 - 2015 Healthline Networks, Inc. All rights reserved for Healthline.