Organolithium Reagents
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Organolithium Reagents


hey it’s professor Dave let’s talk about
organolithium reagents so we’ve talked a little bit about organometallic reagents
such as grignard reagents that’s organometallic because it contains
magnesium magnesium being a metal and so lithium is another metal and so
organolithium reagents which as you might guess are ones that contain
lithium are also organometallic reagents so let’s take a look at how we prepare
them and what they do so we’re gonna start with some alkyl halide right any
3R is a convenient any kind of alkyl halide and we’re going to react with two
lithium atoms so we’re gonna use elemental lithium and we need two
lithium atoms for every molecule of the alkyl halide we’re gonna react in some
non non polar aprotic solvent like hexanes and we’re going to get our
organolithium reagent that’s our organolithium reagent and then the
lithium halide by-product so that is the way that we prepare them and so it’s all
it is it’s some carbon connected to a lithium atom and so here are some
examples of some common organolithium reagents we can have methyl lithium so
that that’s a very common one we can have n butyl lithium where n implies
that it’s a straight chain butyl so we’ve got one two three four lithium and
we can also have tert butyl lithium so here’s the lithium and this is
essentially a tert-butyl group so these are three probably the most common
organolithium reagents and so what are the properties of organic organic
lynnium reagents we remember when when we looked at the grignard reagents right
this is a bit different because we saw that the the magnesium atom would insert
itself into that carbon halogen bond whereas here the lithium simply
displaces it so we’re we don’t have that halogen anymore we just have lithium and
as it happens lithium is even less electronegative than magnesium so
whereas with the with the grignard reagent we saw that we had a partial
minus charge on that carbon because it was a polar bond and carbon was pulling
electron density away from the from magnesium here we see that effect
even more so because lithium is less electronegative than magnesium so this
is an extremely polarized covalent bond this is an extremely this is a very
significant partial minus charge on the carbon so much so that this behaves
almost like a carbon ion it is almost as though this carbon has a formal negative
charge and of course we know that that means that is it is extremely reactive
as a species so what are some things that we can do with these where these
are going to lithium reagents one very common thing is that these are just
sources of nucleophilic carbon again very much like grignard reagents so
here’s an butyl lithium and remember that this carbon attached to the lithium
is the one that bears that very strong partial minus charge almost like a
formal minus charge so this is clearly the nucleophilic carbon so that can come
up here and attack a carbonyl just like a grignard reagent and now we’ve got so
this is the bond that was formed right here right we’ve got one two three four
carbons that’s those four carbons and then these two carbons are right there
and we’ve got that act that oxyanion and then of course any kind of acidic workup
ammonium chloride what-have-you we’re going to be able to protonate and we’re
gonna get our alcohol so this is extremely similar to grignard reagents
we could also do that with a grignard reagent and might want to use this
instead for various reasons but then one big difference is that we typically
would not use a grignard reagent as a base but these organolithium reagents
are excellent basis because carbon ions are very very strong bases right we know
that alkanes are not acidic whatsoever they do not want to lose a proton so if
by any manner you get a carbon ion it desperately wants to get that proton
back to become an alkane and so we can use organolithium reagents as basis so
one common app one common application we talked about how we can deprotonate
terminal alkynes to get that acetylide ion to go do some SN2 do some synthetic
chemistry that way so we can use an organolithium reagent to do that right
we might use sodamide, NaNH2, but we also can use
an organolithium reagent so we can go ahead and get that proton on the
terminal alkyne which is going to produce the acetylide ion so then that
is going to be able to go and attack an alkyl halide do some kind of SN2 do
some more synthetic chemistry so that is a little bit about organolithium
reagents we talked about how they are prepared some common examples of
organolithium reagents the properties of organolithium reagents and then two very
common applications for organolithium reagents.

15 thoughts on “Organolithium Reagents

  1. Very nice, thank you. Synthetic chemistry is kind of hobby and passion. I really get into all the differences and species/compounds that you can create with it. You explained this well. The only is the final link in the chain of the organolitium with deprotonation and the Bronsted–Lowry theory. Maybe a little more on the uses of the final species or the theory itself?? Maybe you have covered it previous, in all honesty I actually just happened upon your channel (glad I did). But overall very well done.

  2. This is not my field of study at all, so honestly I only understood about half of what you covered…which is about a half more than I would have expected to.
    The fact that you helped this make any sense to someone like me says quite a lot. Keep up the great work, Professor!

  3. Sir, Can you explain Methodology and Perspective of Sciences and General Informatics, for Chemistry main students

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