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Lewis Acids and Bases

in this video we're going to talk about

lewis acids and Lewis bases a Lewis acid

is basically an electron pair acceptor a

Lewis base is an electron pair donor so

examples of electron pair acceptor ZAR

ions with positive charges such as H

plus Fe 2 plus al 3 plus these are all

Lewis acids they can accept a pair of

electrons lewis bases our electron pair

donors and any type of ion with a

negative charge like chloride bromide

these are at lewis bases they have

plenty of lone pair electrons to donate

some other examples include hydroxide

iodine water is a lewis base water can

act as a Lewis acid 2 but they can

behave as both they can accept a pair of

electrons or it can donate a pair of

electrons

what is amphoteric it can behave as an

acid or as a base the zinc chloride is

another Lewis acid BH 3 all of these can

accept a pair of electrons febr3 alcl3

these are some other Lewis acids the

methyl carbo cation is a Lewis acid a

carb anion is a Lewis base ammonia is

another Lewis base and so as you can see

Lewis bases they're basically

nucleophiles they're electron rich and

Lewis acids are electrophile

they're electron poor now let's go over

some reactions dealing with Lewis acids

and Lewis bases so consider the reaction

between boron trifluoride and ammonia

ammonia is a Lewis base they can donate

a pair of electrons bf3 that's the Lewis

the boron atom can accept a pair of

electrons so whenever you draw the

curved arrows it's always going to go

from the lewis base to the Lewis acid

and so the product of this reaction is

going to look something like this

a covalent bond is produced nitrogen is

going to have a positive formal charge

and boron is going to have a negative

formal charge so that's the typical

lewis acid lewis base reaction so let's

work on some other examples what's gonna

happen if we put fecl3 and see how -

together you're gonna get fe co4 - but

let's draw it out

so fecl3 like bf3 it has a trigonal

planar shape and this chloride has four

lone pairs and a negative charge and so

it's going to attach itself to the FE

atom and now you're gonna get this so

now the iron atom has a negative formal

charge now let's look at another example

zinc chloride and h2o go ahead and

predict the product of that reaction so

let's draw it out so I'm going to draw

zinc chloride like this and then we're

gonna react it with h2o oxygen has two

lone pairs and so the oxygen atom is

going to attack the zinc atom and we're

going to have a trigonal planar shape

around a zinc atom

so now oxygen only has one lone pair but

now it has a positive charge zinc is now

going to have a negative formal charge

and so that's going to be the product of

that particular lewis acid-base reaction

whenever oxygen has three bonds

it typically bears a positive formal

charge and whenever you add a new bond

to a metal it usually carries a negative

charge

try this example this reaction will be

reversible and you're going to get this

al BR for -

so the bromide ion is going to attack

the aluminum atom and so you're gonna

get a l BR for it has a tetrahedral

molecular geometry and the aluminum atom

now carries the negative charge and so

that's it and that's the basics behind a

lewis acid-base reaction