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General Chemistry

Learn the toughest concepts covered in Chemistry with step-by-step video tutorials and practice problems by world-class tutors

22. Organic Chemistry

Alkane Reactions

The saturated hydrocarbons are referred to as alkanes because of their low polarity and low reactivity. 

Reactions of Alkanes
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Major Reactions of Alkanes

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Hey, guys, In this new video, we're gonna take a look at Al cane reactions. Now, we're gonna say al canes are referred to as Para Fits Okay, which is derived from Latin meaning little affinity here when they say little affinity, that means that they're not very reactive. That's because Al canes are just hydrocarbons. All canes have no pi bonds, no electro negative elements anywhere. So it's non polar, so its main into molecular forces. London dispersion a non polar force. And when it comes to chemistry and reactions, reactions happen best when there is some polarity in the compound. Now we're going to say that Al Keynes really Onley undergo two major types of reactions, one that we've seen from the very beginning of chemistry. Combustion. Remember in combustion are all cane or hydrocarbon reacts with to produce CO two and water so we could have methane gas reacting with 02 gas to produce H 20 Liquid plus Co. Two gas Here we just need to balance it. We have four hydrogen is here, but only two here. So we throw it to and then we have what, two times? One that's two Oxygen's plus another two here is for So I throw it to here so that when we're accustomed to seen now the new one that's connected to organic chemistry, it's called radical catalyzed Halogen nation. So what in the world does that mean? So in radical catalyzed halogen nation, we have an Al cane, a simple arcane. So let's say we have that methane. What we do with this methane is we use X two over heat or light and not just any type of light UV light. And this UV light can be represented by symbol HV. So when you see HV, it just means UV light. And when I say x two x equals C l or B R. And what's happening here is that we're transforming our Al cane into a new compound. And in this reaction, what happens is ah, hydrogen is replaced with a halogen. So one of these hydrogen is one of the four hydrogen will get replaced with, Let's say, C l and we get this new compound. This compound now is polar because it has chlorine is involved. Chlorine is very electro negative, and the thing about this is that this reaction could continue forth even more so we could bring in another mole of X to some mawr heat some more light, and that would replace another hydrogen we can keep bringing in mawr X two more two more heat, more light to replace another and then do it one more time. So at the end, what, we'll have this CCL four as our compound. So you go from methane to methyl chloride. Two methylene chloride. Remember I told you earlier that CH. Two is called methylene methylene chloride to chloroform to finally carbon tetrachloride. So this reaction is just a way of replacing hydrogen with Hala Jin's. And you could either replace just one where you just do mono halogen nation. Or you could just pump in a ton of C L to R B R to a ton of heat a ton of light and replace all the hydrogen on the carbons with Callejon's. That's much harder to do, and usually this reaction on Lee replaces one hydrogen with a halogen. But this would be the organic type of reaction that we're accustomed to seeing. Combustion is a basic type. More Gen. Kim specific. This here's more organic specific. Remember, these are the two major reactions that any al cane can undergo.

One of the major reactions of alkanes is one you should be familiar with:Combustion

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The other alkane reaction is a new one called Radical Catalyzed Halogenation, in which a halogen replaces one of the hydrogens in the alkane. 

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Free Radical Chain Reactions
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Understanding Free Radical Chain Reactions

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Hey guys, let's continue in this new video on talking about radical catalyzed Talaja Nation. So free radical chain reaction or radical catalyzed Talaja Nation all it's really doing here. We're gonna say Under this reaction, a hydrogen from an al cane is replaced by a halogen and the halogen that we usually use our is either bro mean or chlorine. Iodine is too slow and flooring is way too reactive. If Florian tried to form a bond, the compound would actually explode. So we're gonna stay here that in this radical chain reaction Alcan's will undergo will react with diatonic halogen. So cl two or B R. Two in the presence of heat or UV light. And we're gonna say here that when it comes to this process, there are three basic steps to a radical chain reaction. The first step is initiation. Here, a stable compound undergoes home Olynyk cleavage. So home a little cleavage just means so let's say we're dealing with BR. Remember Br Callejon's when not in the center, makes single bonds to one another. Now in home, a little cleavage. The bond between them breaks evenly, each of them brought to the table. One electron and in home Olynyk cleavage that bond breaks in each halogen leaves with the Elektronik came in with. So we go from having zero radicals to having to radicals at the end. What's a radical? A radical is when you have an electron that is not paired, it's just a lone electron. So where's our radical electron? This is our radical electron, and this is our radical electron electrons normally have found paired up. Like all these examples here, they're paired up, but a radical reaction. A radical itself doesn't have an electron to pair up with. Its just by itself. These are extremely dangerous and very active compounds. You hear talks in the news about free radicals, how they damage your skin. This is what they're talking about. The son, actually, because of the UV rays, UV a UV B cause a mutation on your skin where you create free radicals. On the surface, this can lead to cancers, could lead to a lot of different maladies. So this is what they're talking about now in propagation also called the chain reaction step. So when you hear talks of chain reactions, they're talking about the propagation. Step one of these radicals here basically reacts with our Al cane ch four. So we have a radical, a stable compound. They react together to form a new radical and a new stable compound. So basically what happens here is that BR comes in and basically kicks out one of the hydrogen. So now it's ch three br plus the H. I kicked out. So we created a new normal compound in a new radical that is propagation. And in this step, this can happen multiple times, and we can say that this happens multiple times until every single hydrogen would be replaced with a BR. Now it's hard to do this, and usually we just do one model halogen nation. We just usually replace one hydrogen with one halogen, but it is possible to try to replace every single hydrogen here with a br toe wind up with CBR four at the end. But here, if that did happen, your professor would make it clear they would say, Oh, replace all the hydrogen with Callejon's and then finally we have the last step of a radical reaction, which is called termination. Termination is the opposite of initiation initiation. We have one compound breaking up into two radicals. In termination, we have the opposite to radicals combined together to form a new stable compound. So this h radical that got ejected and remember, we only use one of these BR radicals. There's still another one floating around so that h radical in that br radical could somehow find each other and form HBR. So you have to radicals here, each with one UNP aired electron that desperately needs to be paired up. So what did they do? They just meet up and have their electrons form a bond to one another. And so now they're stable. So these are the steps of any radical reaction initiation, propagation, termination. It's important know what their terms mean and also what's most important, what each one forms. So in initiation, we form to radicals. In propagation, we form a radical in a new compound and in termination we get rid of all our radicals to create one new stable compound. So just remember this, and on the next page we'll take a look at different types of radical chain reactions. So remember, all that happens here is we're gonna do mono halogen nation on the following questions. So we're gonna replace Ah, hydrogen with one halogen based on the number of types of hydrogen is present. So take a look at the next questions and then we'll go over them together. So click on the next video and see how I tackle each one.

In a free radical chain reaction an alkane reacts with Br2 or Cland UV light or heat. 

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Determine the major product(s) of the following reaction

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Hey, guys, let's take a look at the examples dealing with radical chain reactions. So here I say, determine the major product or products off the following reaction. So here's what we're gonna see is we have We're just gonna do motto. Um, halogen nation. We're just replacing one hydrogen. Now, both of these are ch threes. So they're both the same meaning that I could replace NH from this end or nature. From this end, it would be the same exact thing. So here we only have one product. I decided to replace it from the end on the right, but again, if we did it on the one on the left would be the same exact thing. So in this reaction to replace one hydrogen with a halogen, that h that got replaced combines with the extra BR that's hanging around. So technically, those would be your two products at the very end. Remember, in mono hallucination, we're looking for the different types of hydrogen is present and replacing them with a halogen. In this one. I want you guys to attempt this one look to see how many different types of hydrogen zehr present. If there's more than one type of hydrogen present. That means you're gonna make a mixture of products more than one possible final product. So if that does exist, show me what those products would look like. Come back, take a look and see how I tackle this question, but first attempted on your own.
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Determine the major product(s) of the following reaction

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Alright, guys. So we're gonna do that radical chain reaction that was left on the bottom of the page. So this one is different than the one above, and the one above it was two ch three is connected to each other. Either one was an end carbon. So they were the same types of hydrogen. But now there is a difference these two or CH threes for the same type. But then we have a CH two in the middle. So that means that these hydrogen is in the middle are different. So there's two possible answers. We can get one where a CEO replaces one of the hydrogen from one of the end carbon hydrogen so we can get this or could have done the left side. It doesn't matter. But then here these air different so it could replace one of those in the middle is well, so your second possible answer could have been this. So remember, in this radical chain reaction, we're trying to replace different types of hydrogen. Here we found that there were two we had ch three hydrogen is and then we had C H two hydrogen. So that gave us two possible answers. Both are possible in terms of being made, so we have to show both of them. And remember, this is the main organic process that we deal with when we're dealing with Al Keynes. When you guys moved to organic, you'll deal with much more complex, um, organic compounds or there'll be more rules introduced. But all of them fundamentally rely on what we've done here today. So just make sure you review this section and see how exactly were able to get two possible answers.
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