Chemical Reactions Essential Chemistry. Chemistry Principles and Practice. Principles of Ionic Organic Reactions. Electrochemical Reactions and Mechanisms in Organic Chemistry. Name Reactions in Heterocyclic Chemistry. Separations and reactions in organic supramolecular chemistry. Chemistry from First Principles. Principles of soil chemistry. Principles of Modern Chemistry. Principles of Food Chemistry. Principles of Polymer Chemistry.
Principles of Environmental Chemistry. Principles of food chemistry. Recommend Documents. From the last video, we know that since this carbon is partially positive, this is the electrophilic center of this compound. If we look at hydroxide ion, which we could have gotten from something like sodium hydroxide, we know that this negatively charged oxygen would be the nucleophilic portion. So hydroxide is gonna act like a nucleophile, and this carbon on our alkyl halide is gonna act like an electrophile.
- Chemistry: Principles and Reactions 7th Edition | Text Book Centre.
- Algebraic structures and operator calculus. Volume II: Special Functions and Computer Science.
- Zumdahl chapter 13.
- Eye Movements from Physiology to Cognition. Selected/Edited Proceedings of the Third European Conference on Eye Movements, Dourdan, France, September 1985.
- Download Chemistry: principles and reactions epub free;
- The Point Of View;
We know that opposite charges attract, so the negatively charged oxygen is going to be attracted to the partially positively charged carbon on the alkyl halide. And we say that the nucleophile attacks the electrophile, so I could draw a curved arrow showing the movement of two electrons over here to this carbon.
At the same time, these two electrons come off onto the chlorine. So the chlorine had three lone pairs of electrons around it, let me go ahead and draw those in. We're gonna add in an extra lone pair of electrons, and let me highlight those electrons in magenta. So these two electrons come off onto the chlorine, so I'll make these this pair. And that gives the chlorine a negative one charge, so this is the chloride anion and we call this a leaving group.
So we're gonna form a bond between the oxygen and this partially positive carbon, so let me say that this lone pair of electrons on the oxygen is gonna form a bond between the oxygen and that carbon. So, on our product, on this alcohol, those two electrons must be these two electrons right here in this bond that formed. So that's a simple organic chemistry mechanism.
We had only one step, the nucleophile attacked and the leaving group left, all in the same step. The goal is not to understand every single thing about this organic chemistry mechanism in great detail right now. Our goal right now is just to appreciate how nucleophiles and electrophiles are used in organic chemistry mechanisms and start to get a feeling for how these curved arrows show the movement or flow of electrons.
Let's look at another organic chemistry mechanism, and we're gonna start by identifying our nucleophile and our electrophile. So let's look at this compound first. We know that oxygen is more electronegative than carbon, so this oxygen is going to withdraw some electron density from this carbon.
And this chlorine is gonna do the same thing because chlorine is more electronegative than carbon too.
So this carbon is electron deficient, right, it is partially positive, and that can act as an electrophile. On the right, we have the acetate anion, which could come from sodium acetate, and this oxygen has a negative one formal charge, so the oxygen is the nucleophilic center of our acetate anion. And our acetate anion can act as a nucleophile. Opposite charges attract, so this negatively charged oxygen is attracted to this positively charged carbon. And we can say that the nucleophile attacks the electrophile and I draw a curved arrow to show the movement of these two electrons.
- Intro to organic mechanisms;
- Go Crochet! Afghan Design Workshop 50 Motifs, 10 Projects, 1 of a Kind Results;
Now, I can't show a bond directly from this oxygen to this carbon until I take these pi electrons and move them off onto the top oxygen here because remember, carbon can never exceed an octet of electrons around it. So let me draw the movement of all of those electrons here. So let's draw, let's draw everything in. So we now would have an oxygen at the top here with three lone pairs of electrons, which give this oxygen a negative one formal charge. So if I'm showing movement of electrons, I'm saying that two electrons from here moved off onto the oxygen, which gives it a negative one formal charge.
I still have this chlorine attached to this carbon, so let me draw in that chlorine down here. So this had three lone pairs of electrons around it. And now we formed a new bond, right, we formed a bond between this oxygen and this carbon. And let me highlight these two electrons in red. So those two electrons in red form a bond between that oxygen and this carbon, and this oxygen still has two lone pairs of electrons around it like that. And now let's draw in the rest of this over here, so we have a carbonyl, so let me draw that in, put in my lone pairs of electrons.
And then, we have a methyl group coming off like that. So the first step of this mechanism is a nucleophilic attack, so let me write first step here. The nucleophile attacks the electrophile. And it turns out this is a two step mechanism, and in the second step of this mechanism, we're gonna get loss of a leaving group. So let's say a lone pair of electrons on this oxygen moves back in to reform a carbonyl, but we cannot exceed an octet of electrons to this carbon.
So that must mean that these two electrons come off onto chlorine, come off onto our leaving group, which would be the chloride anion. Let me draw in those electrons here, which gives the chlorine a negative charge. So the electrons in, let's make them, let's make them blue here, so these electrons in blue come off onto the chlorine to form the chloride anion, which is our leaving group. So we get loss of a leaving group and we reform our carbonyl, which gives us our final product. Again, don't worry too much about the details of the mechanism. Our goal is to identify our nucleophile, electrophile and appreciate our electron flow and start to think about different steps of a mechanism.
Nucleophilic attack is a very common one, so is loss of a leaving group. Let's look at one more organic chemistry mechanism. We're gonna start by identifying our nucleophile and our electrophile. Let's look at this compound first. We know that oxygen is more electronegative than this carbon so the oxygen is going to withdraw some electron density away from that carbon, which makes this carbon partially positive.
Intro to organic mechanisms (video) | Khan Academy
So that's the electrophilic center of this compound. In the first step, we're adding propyl lithium, and we know that carbon is more electronegative than lithium. So carbon's gonna pull these two electrons closer to it, giving this carbon a partially negative charge. Or since the electronegativity difference is so great, we can take those two electrons in that bond and put them on that carbon. So we have three carbons here, and let me draw them in, and we have two electrons on that carbon.
Let me highlight those electrons in magenta.
So these two electrons in magenta go onto that carbon here, which gives this carbon a negative one formal charge. And we have a carbanion. Since we have a negatively charged carbon, this carbanion is an excellent nucleophile, and this is going to attack the electrophilic portion that we already identified.watch
So opposite charges attract and the negative charge is attracted to the positive charge. And in the first step of our mechanism, our nucleophile attacks our electrophile. Now, we can't just show a bond between those two carbons because that would give 10 electrons around this carbon, right, that would exceed an octet of electrons. So we have to show some electrons going somewhere else. We can take these two electrons and move them off onto our oxygen. So in our first step, our nucleophile attacks our electrophile, and we form a carbon-carbon bond.
So we also have an oxygen here with three lone pairs of electrons around it, which give it a negative one formal charge, so we can follow some of those electrons, let me make them blue here. So these electrons come off onto our oxygen, giving the oxygen a negative one formal charge.