oh okay so welcome back to organic chem chemistry 2 this is just a supplemental video um um as requested by some students a few years ago um people are getting a bit confused about arrows there's different types curly arrows reaction arrows equilibrium arrows resonance arrows um and this is just a very quick and quick and easy guide into them so what is a curly Arrow a curly Arrow shows the movement of a pair of electrons from something with a high energy density electron density to something with low electron density so from a nucleophile to an electrophile so we a curly arrow with that the Arrow Head that looks like this showing that movement of that pair of electrons from here to the electrophile here so this one has electrons to share this one welcomes electron so this is this nucleophile wants to find a nucleus so it's nucleus loving nucleophilic this one electrophile loves electrons so wants these electrons to be shared to it you never draw these arrows in the other direction so you're going from a nucleophile to an electrophile you can only share something if you already have it so a nucleophile has that pair of electrons it can share it so it can then push your showing you're sharing those electrons and pushing them over here generally forming a bond between the two and what we see in our case most of the times a nucleophile is attacking a carbon not always but um and again a reminder nucleophiles can attack everything except for hydrogen okay so you'll see often in text books like this e with little Accent on it that can stand for electrons or electros so sometimes you'll see electrophile written as eile or electron pair e pair okay it's just a Shand way so nucleophiles here we go donate electrons from the available high energy orbitals okay so it's got a lone pair and you'll see it happening from a lone pair on a nucleophile so maybe you might see ammonia there's a NH3 with a lone pair on the top of it um you could have a negative charge okay so it's going from the negative charge it could be from a double bond like a pi bond from an Al you can actually share that pair of electrons from that that alken Bond or a sigma bond to an electropositive atom so organometallics um for instance now that's probably not something you've seen yet but just so you know and electrophiles accept electrons there's our little symbol there into their empty low energy orbital okay that's maybe a little bit above what we're doing on first year but let's just put it out there anyway so you can push your electron pair into something with a positive charge like a an empty orbital so C+ right a neutral molecule that has an empty p orbital to accept it um you could actually push it from a double bond to an electron negative element so for this double bond pushing it onto that oxygen um or a single bond to an electr negative element so we could actually take that single Bond and push that pair of electrons onto that chloro chlorine to form a chloride okay so there's different ways of doing it this might be a little bit above what you're doing in first year but it might be a good primer for when you go into second year so nucleophiles donate electrons to electrophiles and electrophiles accept electrons from nucleophiles please please please never draw your curly Arrow in this direction this has there's no look at there's no electrons there's no electron pair here to share you can't share where you don't have okay and this this nucleophile doesn't want more electrons coming its way it wants to push its electrons in this away okay now you might see sometimes a curly arrow that looks like a fish hook do not use a fish hook for this a fish hook means the movement of a single electron and we're showing a movement of a pair of electrons so you'll get into this in I don't know if you do it in first year second year you start looking at radical chemistry so moving a single electron but we're not using that here so often you see this curly Arrow from a negative charge going to a positive charge it's really short hands for showing that pair of electrons going to the positive charge so when you drawing your curly Arrow you have to always start on something to represent that pair of electrons so it could be a negative charge so we just saw that above here we go it could be a lone pair like we see that it could be a bond like a double bond or even a single Bond you're showing that pair of electrons in something is moving so that's the reason the pointy end has to point where you're going and don't be vague okay I'm not asking you to draw curly arrows but you need to know how to do this okay so you're showing where you're moving those electrons to you'll find that if you have charges if you ever have to draw them Circle them it makes it easier to see now we talking about Curly arrows but you've seen other arrows too you've seen reaction arrows that look like this it's just show going from reactants to products starting materials to products okay this is an equilibrium so this is yeah um showing that two species are interchanging and I think we've seen like H2O to H+ and oh H minus that's an equilibrium equilibrium Arrow it's going back and forth oh look this's my example in front of us oh minus pushing it pair of electrons onto that proton equilibrium arrow and then we form water but if we break that Bond and push those pair of electrons here we go back here and reform this so that's an equilibrium we're looking at it sitting back and forth if you see an arrow that has this double-ended arrow that means a resonance Arrow now we're going to see that more in aromatic chemistry so we're going to be showing how two forms are sort of uh um pushing electrons back and forth so look at look at this here's a positive charge here we're going to push those electrons here resonance Arrow it's the same thing as this we push it back here it comes back here comes back there comes back here so really what it is is sharing this electrons across both of these bonds so this hopefully will make more sense when we do our aromatic chemistry section um and just to point out that when you do have these arrows you are conserving charge in each step of the reaction so here is chlorine it's seven veence electrons you're adding an extra electron into it so there's a negative charge there so you form a chloride anion here and there's that extra electron that if you add it in there that negative charge up here is showing you that you have one electrons too many okay so that negative charge means you have one electron in excess or if it's two minus there's two electrons on there in excess of the nuclear charge um this is the end of this section this might be a little bit over your head or not but for those of you are curious it's just a good entry point