Organic Chemistry - Synthesis of Aldehydes and Ketones
Summary
TLDRThis chemistry lesson delves into the synthesis of ketones and aldehydes from various molecular structures, including primary alcohols, secondary alcohols, alkenes, benzene rings, alkynes, carboxylic acids, nitriles, and esters. It highlights the importance of selecting appropriate reagents and conditions to achieve the desired products, such as using mild oxidizing agents like PCC or DMP for primary alcohols, and the Gattermann-Koch reaction for benzene rings. The script also touches on ozonolysis for alkenes and the reduction of nitriles and esters to form aldehydes, offering a comprehensive guide to organic synthesis techniques.
Takeaways
- đ§Ș The lecture discusses the synthesis of ketones and aldehydes from various organic molecules using specific reagents.
- đŸ Primary alcohols can be oxidized to aldehydes using mild oxidizing agents like PCC, DMSO, or DMP to avoid over-oxidation to carboxylic acids.
- đ To convert an aldehyde to a ketone, a two-step process involving a Grignard reagent (RMgX) and subsequent oxidation is described.
- âïž Secondary alcohols can be directly oxidized to ketones using either mild or strong oxidizing agents, with caution to avoid over-oxidation to carboxylic acids.
- đŹ Ozonolysis, involving ozone and DMSO, is a method to cleave alkenes to yield ketones and formaldehyde, a special type of aldehyde.
- đ” The Friedel-Crafts acylation is a technique to introduce a ketone group onto a benzene ring using acyl chloride and aluminum chloride as a catalyst.
- đ Gattermann-Koch synthesis is an alternative method for creating an aldehyde on a benzene ring using carbon monoxide, hydrochloric acid, and a catalyst under high pressure.
- đ Adding mercury ion, sulfuric acid, and water to an alkyne can result in the formation of an enol, which readily tautomerizes to a ketone through Markovnikov addition.
- đ To create an aldehyde from a carboxylic acid, one can first convert it to an acid chloride and then reduce it using a mild reducing agent like lithium tri-tert-butoxyaluminum hydride.
- đŸ The Grenald reaction is used to convert nitriles to ketones by adding a Grignard reagent followed by an acid to hydrolyze the intermediate imine.
- 𧎠DIBAL-H (Diisobutyl aluminum hydride) is a reagent that can be used to reduce esters to aldehydes in a one-step process.
Q & A
What is the primary goal of the video script?
-The primary goal of the video script is to cover the synthesis of ketones and aldehydes from various types of molecules using appropriate reagents.
Why can't a primary alcohol be directly converted into a ketone?
-A primary alcohol cannot be directly converted into a ketone because oxidation of a primary alcohol typically leads to an aldehyde or a carboxylic acid, not a ketone.
What is a mild oxidizing agent that can be used to convert a primary alcohol into an aldehyde?
-Mild oxidizing agents such as PCC (Pyridinium Chlorochromate), DMSO (Dimethyl Sulfoxide), or DMP (Dess-Martin Periodinane) can be used to convert a primary alcohol into an aldehyde.
What is the process of converting an aldehyde to a ketone, as described in the script?
-The process involves reacting the aldehyde with a Grignard reagent (RMgX), followed by the addition of an acid to remove the magnesium ion, and then re-oxidizing the intermediate to form the ketone.
How can a secondary alcohol be converted into a ketone?
-A secondary alcohol can be converted into a ketone using either mild reagents like PCC or strong oxidizing agents like mercuric acid (Hg(OAc)2), provided that the alcohol is on a secondary carbon.
What is ozonolysis and how is it used to synthesize ketones and aldehydes from alkenes?
-Ozonolysis is a reaction where ozone (O3) is added to an alkene in the presence of DMSO (Dimethyl Sulfoxide). This cleaves the double bond in the alkene, replacing the bonds with oxygen to form a ketone and an aldehyde, specifically formaldehyde in some cases.
What is Friedel-Crafts acylation and how is it used to create a ketone on a benzene ring?
-Friedel-Crafts acylation is a reaction where an acyl chloride (RCOCl) is added to a benzene ring in the presence of a catalyst like aluminum chloride (AlCl3). This results in the formation of a ketone on the benzene ring.
How can an alkyne be converted into a ketone or an aldehyde?
-An alkyne can be converted into a ketone by adding a mercury ion (Hg2+) and sulfuric acid (H2SO4), which leads to the formation of an enol intermediate that tautomerizes to a ketone. For an aldehyde, anti-Markovnikov addition using diisobutylaluminum hydride (DIBAL-H) followed by oxidation with hydrogen peroxide and sodium hydroxide (NaOH) is used.
What is the process of converting a carboxylic acid into a ketone or an aldehyde?
-A carboxylic acid can be converted into a ketone by adding two equivalents of an alkyl group connected to lithium (RLi). To form an aldehyde, the carboxylic acid is first converted into an acid chloride using thionyl chloride (SOCl2), and then reduced using lithium tri-tert-butoxyaluminum hydride (LiAl(OtBu)3H).
How can a nitrile be converted into a ketone or an aldehyde?
-A nitrile can be converted into a ketone by adding a Grignard reagent (RMgX) and then acidifying to hydrolyze the intermediate imine. To form an aldehyde, diisobutylaluminum hydride (DIBAL-H) is used to reduce the nitrile directly.
What is the role of diisobutyl aluminum hydride (DIBAL-H) in the synthesis of aldehydes?
-Diisobutyl aluminum hydride (DIBAL-H) is used as a reducing agent to convert esters and acid chlorides into aldehydes by selectively reducing the carbonyl group.
Outlines
đ§Ș Synthesis of Ketones and Aldehydes from Alcohols
This paragraph discusses the conversion of primary and secondary alcohols into ketones and aldehydes using various reagents. Primary alcohols can be oxidized to aldehydes using mild oxidants such as PCC, DMSO, or DMP. To form a ketone from an aldehyde, a two-step process involving Grignard reagent and re-oxidation with mild reagents or mercuric acid is described. The situation is reversed for secondary alcohols, which can be directly oxidized to ketones using either mild or strong oxidizing agents, with caution advised to avoid over-oxidation to carboxylic acids.
đ Organic Reactions with Alkenes and Benzene Rings
The paragraph covers the synthesis of ketones and aldehydes from alkenes and benzene rings. Ozonolysis is presented as a method to cleave double bonds in alkenes, yielding ketones and formaldehyde, a special type of aldehyde. For benzene rings, Friedel-Crafts acylation is introduced to attach an acyl group, resulting in ketones. An alternative method for synthesizing aldehydes on benzene rings, the Gattermann-Koch synthesis, is also discussed, involving carbon monoxide, hydrochloric acid, and a catalyst under high pressure.
đ Advanced Synthesis Techniques for Alkynes and Carboxylic Acids
This section delves into the synthesis of ketones and aldehydes from alkynes and carboxylic acids. For alkynes, a method involving mercury ion, sulfuric acid, and water is described, which leads to the formation of an enol and subsequently a ketone. Anti-Markovnikov addition is also discussed, using a different set of reagents to achieve the desired aldehyde. Carboxylic acids can be converted to ketones through the addition of organolithium compounds, while a more complex process involving acid chloride and a specific reducing agent is required to synthesize aldehydes from carboxylic acids.
đ ïž Nitrile and Ester Transformations to Ketones and Aldehydes
The final paragraph addresses the synthesis of ketones and aldehydes from nitriles and esters. Nitriles can be converted to ketones through a Grignard reaction and to aldehydes using diisobutyl aluminum hydride. For esters, while there is no direct method to create a ketone, an aldehyde can be synthesized using the same reducing agent as for nitriles. The paragraph concludes with a note on the importance of understanding the mechanisms behind these synthetic processes.
Mindmap
Keywords
đĄKetones
đĄAldehydes
đĄPrimary Alcohol
đĄSecondary Alcohol
đĄOzonolysis
đĄFields Craft Acylation
đĄGattermann-Koch Synthesis
đĄAlkynes
đĄCarboxylic Acid
đĄNitriles
đĄEsters
Highlights
Introduction to the synthesis of ketones and aldehydes from various molecules using appropriate reagents.
Primary alcohols can be oxidized to aldehydes using mild oxidizing agents like PCC, DMSO, or DMP.
Conversion of aldehydes to ketones through the Green Art reaction with Grignard reagents and acid.
Secondary alcohols can be directly oxidized to ketones using mild or strong oxidizing agents.
Ozonolysis is a method for converting alkenes into ketones and formaldehyde through the cleavage of double bonds.
Field's craft acylation is a technique for synthesizing ketones on a benzene ring using acyl chloride and aluminum chloride.
Gattinger-Koch synthesis is an alternative method for creating aldehydes on a benzene ring using carbon monoxide and hydrochloric acid under high pressure.
Alkynes can be converted to ketones through the addition of mercury ions, sulfuric acid, and water, resulting in an enol that tautomerizes to a ketone.
Anti-Markovnikov addition for alkynes involves the use of DIBAL-H and subsequent oxidation with hydrogen peroxide and sodium hydroxide to form aldehydes.
Carboxylic acids can be transformed into ketones by adding two alkyl groups using organolithium reagents.
Conversion of carboxylic acids to aldehydes involves creating an acid chloride and then reducing it with lithium tri-tert-butoxide aluminum hydride.
Nitriles can be converted to ketones through a Grenard reaction, forming an imine intermediate that hydrolyzes to a ketone.
Diisobutyl aluminum hydride (DIBAL-H) is a reagent used to convert nitriles to aldehydes.
Esters can be indirectly converted to ketones, but there is no direct method; aldehydes can be formed using DIBAL-H.
In the case of cyclic esters, DIBAL-H results in an aldehyde with an alcohol group due to the ring structure.
Emphasis on the importance of understanding the mechanisms for the practical applications of these synthetic methods.
Transcripts
hello and welcome back to organic
chemistry today we will be covering
synthesis of ketones and aldehydes we
will look at many different molecules
and try to convert them into ketones and
aldehydes
using the appropriate reagents we will
not be covering the mechanism so i
advise you to look at the mechanisms on
your own later
as for now let's start off with our
first molecule over here
here we have our primary interest is our
primary alcohol on this alkane
and what we want to do with this alcohol
is try to convert to either a ketone or
an aldehyde
now since it's a primary alcohol can we
change it into a ketone
well sadly no if we try to oxidize this
alcohol it'll either turn to an aldehyde
or a carboxylic acid and so to change it
into an aldehyde
we have to oxidize it now if you provide
too strong of an oxidizing agent you
just create a carboxylic acid
and so we don't want to do that we want
to have a mild oxidizing agent
and our possible reagents is either pcc
either dmso or we can use dmp
and we can use either of these they will
work just fine in creating an aldehyde
and our product would look something
like this
now if we really wanted that ketone what
we could do
is actually react this aldehyde with
step one a green art where r over here
represents any alkyl group
magnesium and x represents a halite then
we can add an acid in order to
remove the magnesium from the oxygen ion
that would have a negative charge on it
and then we can
re-oxidize it again and we can use
either
either of these mild reagents or we can
use something
like hg so4 and
h2 so4 and if you recognize what this is
this is a combination to create mercuric
acid and that will create
this ketone right here and r is the r
group that we added from the
greenhouse reagent so that is one way to
create a ketone
from primary alcohol however notice that
you are adding
extra alkyl groups to it in order to
perform this
now if we have a secondary alcohol the
situation flips
can we create a ketone from this well
yes we can and we can use either
our mild reagents or we can use a strong
reagent
and we can just use mercuric acid is one
and it's a real this is considered a
strong oxidizing agent
so be careful when using this make sure
that it is a secondary carbon or
secondary alcohol that we have over here
and that will make sure that it only
turns into ketone if you use mercuric
acid
on something like a primary alcohol
you'll just create a carboxylic acid
so over here we have our ketone
now can we change this into an aldehyde
well sadly we can't because this is a
secondary
carbon in order to have an aldehyde we
have to have a primary carbon and that's
it
now let's look at our next molecule
over here we have an alkene
now what can we do with an alkene well
there is one method
in order to create either ketone or an
aldehyde but that would only depend on
the substituents that we have over here
on one side of this alkene we have two
carbon bonds and the other side we have
hydrogens and that's it
and so what we could do is do something
called ozonolysis
and if we create if we add ozone along
with dmso
which is dimethyl sulfoxide what that
happens is it cleaves that middle bond
in between the two carbons and basically
replaces
the bonds that the carbon was missing
with an oxygen
and so we get a ketone over here
plus an aldehyde
and this is actually a special type of
an aldehyde an aldehyde with no carbon
bonds at all is called formaldehyde it's
actually pretty unstable
but this oils analysis basically cleaves
that middle bond
and it makes sure that even if you have
only
one carbon bond or actually no carbon
bonds at all you will not get a
carboxylic acid you will simply just get
a ketone or an aldehyde it's a mild form
of alkene cleavage and this is one
this is one way you can get ketones and
aldehydes from double bonds
now let's look at a benzene if we have a
benzene ring
can we create a ketone aldehyde well yes
we can now how do we get
create a ketone one way to do this
is called uh fields craft acylation
and what we do is provide this benzene
with an acyl chloride with that or
acid chloride is something like say now
what this looks like
is you have our double a carbonyl group
connected to a chloride instead of an
uh a hot oxygen and a hydrogen
and then we have any r group which is
can be any alkyl group
and then if you add this with aluminum
chloride which will be our catalyst
what ends up creating what ends up
happening is we add
this acyl group onto the benzene and it
gets rid of that chloride and we just
get this product right here
and if you notice this is a ketone
now what if we wanted an aldehyde say
this r group that we wanted over here
would be a hydrogen how would we do that
well there's a different method we can't
just use
um an acyl chloride that looks like this
that's not right here this is extremely
unstable
this type of acyl chloride is not stable
enough for us to use and so we have to
use a different method
and what we do is use these following
regions we use carbon monoxide
we use hydrochloric acid and this is
under high pressure
then we have aluminum chloride and
we also have copper chloride
the carbon monoxide and hydrochloric
acid is what will create that
specific molecule i just showed you
that's pretty unstable and the aluminum
chloride and copper chloride will help
um catalyze this reaction and what we'll
just create
is this benzene ring with instead
of an r group we have a hydrogen
and so this is called the gattering
constant synthesis
and so this is one way of creating an
aldehyde on a benzene ring
now let's look at our next example over
here we have an
alkyne how do we create ketones and
aldehydes from an alkyne well
to create a ketone we can do something
where we add a mercury ion
we add sulfuric acid and we add some
water
and when you do that what this does is
it adds basically
an oh group to one of the carbons and
hydrogen to the other carbon and these
are the carbons containing that
alkyne and what this creates is this
transition state where we have something
called an enol which is basically
an alcohol group on a double bond
and this is extremely unstable so just
instantly total rises to some
to just a ketone and that's it now
notice that this is markovnikov addition
the hydrogen is being added to the
carbon that has the more hydrogens
and the alcohol group
is being added to the carbon that's more
substituted
now if we wanted to do it the other way
around what would end up happening is ha
if we wanted this double carbonyl group
to be on the edge
it would be the anti-markovnikov
addition and so to do that we have to do
something else our first step would be
to add
siamo or diasymal borohydride or boring
and then our second step would be to add
hydrogen peroxide and sodium hydroxide
naoh and this does the same process
where we get that transition state for
the enol but instead
the enol has the alcohol on the carbon
with the most amount of hydrogens the
less substituted one and this just
creates
our preferred aldehyde that we wanted to
look for
and so that's an alkyne and that's how
you can create either a ketone or
aldehyde notice that this is markovnikov
addition in the first step
the other one is anti-markovnikov now
for our second one we have a carboxylic
acid how do we change a carboxylic acid
into a ketone or an aldehyde well our
first step
to change it to a ketone would be to add
two alkyl groups connected
or two equivalences of an alkyl group
connected to a lithium
this is basically called an
organolithium where r over here
represents any alkyl group
and if we add this essentially
we have something that's very similar to
a greener
reaction but not quite and we get this
product right here it's a ketone and the
r group is connected
to that carbonyl now if we wanted
to do an aldehyde if we want to create
an aldehyde is that possible well
it is well actually not directly though
if we want to create an aldehyde we
cannot
simply just go straight to it but there
is something else that we know
we can change this carboxylic acid into
an acyl chloride or an acid chloride
if we have thymic chloride added to it
when is this happening is that we have
the carboxylic acid essentially but the
oh group is replaced with a chlorine
now this right here can actually be more
useful
in creating an aldehyde because since we
can't go to an aldehyde replace from a
carboxylic acid
what we can do here is change this into
either a ketone or an aldehyde
now if we want to create a ketone this
is just another way of creating ketones
from a carboxylic acid an
indirect way we can have
an r group over here and two of them
actually
connected to a copper and lithium and
this is called lithium
cuberate this is what that is and when
we add that we simply just create
this ketone right here in our group and
this looks exactly the same as if we
just added
two equivalences of an organolithium
it's just an indirect way
and if we want to create an aldehyde in
this situation it is possible
and to do so we have this reagent right
here and if you notice let me write it
out because it has a pretty long name
but i'll show you what's kind of
interesting about it
now notice how this is similar to
lithium aluminum hydride
but instead of having four hydrogens you
only have one hydrogen and you have this
group right here
now the name of this now changes to
lithium
triter butoxide aluminum hydride this is
the full name of it
and just a milder version of a lithium
aluminum hydride lithium
anhydride would be way too strong of a
reducing agent
and so it would just take it straight to
an alcohol and so this is a more milder
version
and this will give us our aldehyde
now notice this is useful on the acid
chloride because acid core it's a lot
more easy to reduce than a carboxylic
acid
and so this is your method in creating
an aldehyde from a carboxylic acid you
create an acid chloride
and then you change that to an aldehyde
now let's look at our next group
if we have a nitrile how do we create a
ketone
or an aldehyde well to create a ketone
what we do is we do a grenard reaction
we simply add
the green art reagent and then
afterwards we just add the acid
and then after that third and then
that's it
now remember how we had that primary
alcohol where when we changed the
aldehyde
after we changed the aldehyde we created
a ketone by doing the greenhouse
reaction
and our third step was oxidizing it one
more one
once more well in this scenario we don't
when we add that reynard reagent what
ends up happening is we create an imine
which is nitrogen with two bonds with a
double bond
and this acid will hydrolyze it and just
change it into a ketone
and so we just get this product right
here
and notice i label these carbons as a
and b these are the same carbons
a and b and so the carbon that used to
have a triple bond to a nitrogen now has
a double bond to an oxygen
now if we want to create an aldehyde
from this one way to do this
is by using this region right here let
me write it up first and then we'll say
what its name is
now this right here is called di
isobutyl aluminum hydride or
a shorter way to write it is this
double h or diacetyl aluminum hydride
and this essentially creates an aldehyde
of this nitrile
that looks just like this and our
carbons a and b are look right here
so that's what we can do with nitrile
it's pretty straightforward
now our next group that we're going to
look at is an ester can we create a
ketone or an aldehyde from ester
well if we wanted to create a ketone we
actually can
there's no direct way to do it there are
indirect methods like we had when we had
our primary alcohol
where we can simply create an aldehyde
and then create a ketone afterwards
now the first question is though can we
actually create an aldehyde
well we can if we want to create an
aldehyde we use the same reagent we just
covered a second ago
which is diisobutyl aluminum hydride
and this will essentially create this
aldehyde right here
where the group that existed
right here is now no longer attached
to our carbonyl group now say if we had
a ring
say for example we had some group like
this where we have
a carbonyl group like that if we end up
using
diisobutyl aluminum hydride
this would give us this product right
here we have our aldehyde obviously
and we have our carbons but then this
oxygen that we had over here
is no longer gone it's just an oh group
at this point so
it's not like this group is completely
gone if we have a ring
you realize that this is a connected
structure
and the oxygen oxygen that was and part
of
the ester group is now an alcohol
and so that is all for today make sure
you do cover
the mechanisms for all of these these
are really useful
but that is all for synthesis have a
great day
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