PREPARATION OF ALDEHYDES AND KETONES /CLASS 12
Summary
TLDRIn this chemistry session, Anita Raj teaches the preparation of aldehydes and ketones through oxidation processes. She explains how primary alcohols like ethyl alcohol can be oxidized to form aldehydes using acidified potassium dichromate, with controlled conditions to prevent further oxidation. Secondary alcohols are converted to ketones in a similar manner. The video also covers the production of aldehydes and ketones from alkenes through reductive ozonolysis, hydration of alkynes, catalytic hydrogenation of acid chlorides, and dry distillation of calcium salts of carboxylic acids. Additionally, aldehydes can be produced from nitrites via the Stetten reduction process.
Takeaways
- đ§Ș Aldehydes and ketones can be prepared by controlled oxidation processes.
- đĄ Primary alcohols are oxidized to aldehydes using acidified potassium dichromate in a controlled manner to prevent further oxidation to carboxylic acids.
- đ Ethyl alcohol specifically yields acetaldehyde when oxidized with acidified potassium dichromate.
- đ Secondary alcohols, like isopropyl alcohol, are oxidized to ketones under similar conditions, resulting in compounds like acetone.
- âïž Unsymmetrical alkenes undergo reductive ozonolysis to produce two different aldehydes, while symmetrical alkenes yield only one type.
- đ Aldehydes can be obtained from alkenes without branching at the carbon atoms involved in the double bond.
- đ„ Alkynes, like acetylene, can be hydrated to produce aldehydes, with an intermediate unstable vinyl alcohol forming and then transforming into acetaldehyde.
- đ Ketones are produced from alkenes with branching at the carbon atoms involved in the double bond through reductive ozonolysis.
- âïž Acid chlorides can be reduced to aldehydes and ketones using different methods, including catalytic hydrogenation and reactions with dimethylcadmium.
- đŹ Aldehydes and ketones can also be derived from carboxylic acids through the dry distillation of their calcium salts.
- đ§Ș Stiff's reduction involves the partial reduction of nitriles to aldehydes using zinc and hydrochloric acid at specific temperatures.
Q & A
What is the controlled oxidation process for preparing aldehydes?
-The controlled oxidation process for preparing aldehydes involves the use of acidified potassium dichromate, which is potassium dichromate in the presence of sulfuric acid. This process oxidizes primary alcohols, such as ethyl alcohol, to aldehydes like acetaldehyde (CH3CHO), with the removal of hydrogen as water.
Why is the oxidation of primary alcohols to aldehydes a controlled process?
-The oxidation of primary alcohols to aldehydes must be controlled because if it proceeds without control, the aldehyde can further oxidize to a carboxylic acid. It's important to remove the aldehyde from the reaction mixture as soon as it forms to prevent further oxidation.
How are ketones produced from secondary alcohols?
-Ketones are produced from secondary alcohols through oxidation using acidified potassium dichromate. For example, isopropyl alcohol undergoes oxidation, leading to the removal of hydrogen as water and the formation of a ketone such as acetone (CH3COCH3).
What is reductive ozonolysis and how does it produce aldehydes?
-Reductive ozonolysis is a process where alkenes react with ozone to form an ozonide intermediate, which then reacts with zinc dust in the presence of water to produce aldehydes. This method is used for alkenes without branching at the carbon atoms involved in the double bond.
How does the symmetry of an alkene affect the type of aldehydes produced in reductive ozonolysis?
-The symmetry of an alkene determines the types of aldehydes produced in reductive ozonolysis. Unsymmetrical alkenes yield two different aldehydes, while symmetrical alkenes yield the same type of aldehyde.
What is the role of zinc in the reductive ozonolysis process?
-In the reductive ozonolysis process, zinc reacts with the oxygen from the ozonide intermediate, forming zinc oxide and reducing the ozonide to an aldehyde.
How are ketones produced from alkenes with branching?
-Ketones are produced from alkenes with branching at the carbon atoms involved in the double bond through reductive ozonolysis. The branching leads to the formation of ketones rather than aldehydes upon ozonolysis and reduction.
What is the hydration of alkynes and how does it lead to the formation of aldehydes?
-The hydration of alkynes involves passing alkynes, such as acetylene, through dilute sulfuric acid in the presence of mercuric sulfate, leading to the formation of aldehydes like acetaldehyde (CH3CHO). This process involves the addition of water across the triple bond.
How are aldehydes and ketones produced from acid chlorides?
-Aldehydes can be produced from acid chlorides by catalytic hydrogenation in the presence of a palladium catalyst supported by barium sulfate. For ketones, acid chlorides are treated with dimethyl cadmium in dry ether to produce ketones like acetone (CH3COCH3).
What is the significance of using a poisoned catalyst in the hydrogenation of acid chlorides?
-Using a poisoned catalyst, such as one partially poisoned with sulfur, prevents the over-reduction of aldehydes to alcohols, ensuring that the desired aldehyde product is obtained and not further reduced.
How are aldehydes and ketones produced from the dry distillation of calcium salts of carboxylic acids?
-Aldehydes and ketones can be produced by dry distillation of calcium salts of carboxylic acids. For example, calcium acetate undergoes dry distillation to produce acetaldehyde (CH3CHO), while calcium salts of other carboxylic acids can produce ketones.
What is the Stiff reduction and how is it used to produce aldehydes?
-The Stiff reduction is a process where nitriles are partially reduced to aldehydes using zinc and hydrochloric acid at specific temperatures. This method involves the conversion of nitriles to imine hydrochlorides, which upon boiling with water yield aldehydes.
Outlines
đ§Ș Preparation of Aldehydes and Ketones
This paragraph discusses the preparation of aldehydes and ketones through oxidation processes. Aldehydes are produced from primary alcohols like ethyl alcohol using acidified potassium dichromate, with careful control to prevent further oxidation to carboxylic acids. The process involves the removal of hydrogen atoms to form a water molecule, resulting in acetaldehyde. Ketones are obtained from secondary alcohols, exemplified by the oxidation of isopropyl alcohol to acetone. The paragraph also covers the preparation of aldehydes and ketones through reductive ozonolysis of alkenes, distinguishing between symmetrical and unsymmetrical alkenes and the resulting products. The process involves the reaction of alkenes with ozone to form intermediate ozonides, which upon reduction with zinc dust, yield aldehydes. The paragraph concludes with a mention of further topics to be covered in upcoming sessions.
đĄïž Advanced Synthesis of Aldehydes and Ketones
The second paragraph delves into more advanced methods of synthesizing aldehydes and ketones. It begins with the preparation of ketones from alkenes with branching at the double-bonded carbon atoms, using 2,3-dimethyl-2-butene as an example. The process involves ozonolysis followed by reduction with zinc dust to yield two molecules of acetone. The paragraph then explores the hydration of alkynes to produce aldehydes, using acetylene and mercuric sulfate in dilute sulfuric acid to form acetaldehyde. It also discusses the preparation of ketones from other alkynes under similar conditions. The section concludes with the production of aldehydes and ketones from acid chlorides through catalytic hydrogenation, with acetyl chloride used as an example. The use of a palladium catalyst and the importance of poisoning the catalyst with sulfur to prevent over-reduction to alcohols is highlighted.
đŹ Further Methods for Aldehydes and Ketones Production
The final paragraph covers additional methods for producing aldehydes and ketones. It starts with the production of aldehydes from the dry distillation of calcium salts of carboxylic acids, using calcium acetate and calcium formate as an example. The process results in the formation of acetaldehyde and calcium carbonate. The paragraph then discusses the production of ketones from the dry distillation of calcium salts of carboxylic acids, again using calcium acetate as an example, which yields ketones and calcium carbonate. The section concludes with the preparation of aldehydes from nitrites through the Stoffenstein reduction, a partial reduction process involving zinc and hydrochloric acid. The process converts methyl cyanide to an adduct, which upon boiling with water, yields acetaldehyde and ammonium chloride. The paragraph ends with a sign-off, indicating that further topics will be discussed in future sessions.
Mindmap
Keywords
đĄAldehydes
đĄKetones
đĄOxidation
đĄAcidified Potassium Dichromate
đĄReductive Ozonolysis
đĄAlkenes
đĄAcetaldehyde
đĄAcetone
đĄHydration
đĄAcetyl Chloride
đĄCatalytic Hydrogenation
Highlights
Introduction to the session on aldehydes, ketones, and carboxylic acids.
Preparation of aldehydes and ketones through oxidation using acidified potassium dichromate.
Conversion of primary alcohols to aldehydes, exemplified by the oxidation of ethyl alcohol to acetaldehyde.
Importance of controlled oxidation to prevent further oxidation of aldehydes to carboxylic acids.
Removal of aldehydes by distillation immediately after formation to prevent further oxidation.
Preparation of ketones from secondary alcohols, demonstrated by the oxidation of isopropyl alcohol to acetone.
Explanation of reductive ozonolysis of alkenes to produce aldehydes.
Difference between symmetrical and unsymmetrical alkenes in reductive ozonolysis and the resulting aldehydes.
Production of two different aldehydes from unsymmetrical alkenes, such as propylene.
Formation of ketones from alkenes with branching at the carbon atoms involved in the double bond.
Conversion of alkynes to aldehydes and ketones through hydration.
Use of mercuric sulfate and dilute sulfuric acid in the hydration of acetylene to produce acetaldehyde.
Intermediate product formation during hydration of alkynes and its transformation to aldehydes.
Preparation of ketones from other types of alkynes besides acetylene.
Conversion of acid chlorides to aldehydes and ketones through catalytic hydrogenation.
Role of palladium catalyst and its poisoning with sulfur to prevent over-reduction to alcohols.
Production of aldehydes from acid chlorides using dimethyl cadmium in dry ether.
Preparation of aldehydes and ketones from the dry distillation of calcium salts of carboxylic acids.
Formation of acetaldehyde from calcium acetate and calcium formate through dry distillation.
Stoichiometric reduction of nitriles to aldehydes using zinc and hydrochloric acid.
Conversion of methyl cyanide to acetyl chloride through reduction and subsequent hydrolysis.
Summary of the methods for preparing aldehydes and ketones discussed in the session.
Transcripts
[Music]
hi hello this is anita raj your
chemistry mentor welcoming you for one
more session in aldehydes ketones and
carboxylic acids in this session i shall
teach you the preparation of aldehydes
and ketones by oxidation process it is
possible to prepare aldehydes and
ketones that do in a controlled manner
by using acidified potassium dichromate
okay so let us see how aldehydes are
prepared first see these aldehydes are
prepared from the primary alcohol so i
have taken ethyl alcohol now see this
ethyl alcohol undergoes oxidation in the
presence of acidified potassium
dichromate that means potassium
dichromate in the presence of sulfuric
acid understood so what happens is see
uh this alcohol this under goes
oxidation so one hydrogen from this
carbon and the next hydrogen will be uh
removed as a water molecule okay and
finally we'll be getting acetaldehyde
ch3cho so we are getting acetaldehyde
from ethyl alcohol understood why this
reaction has to be taken place in a
controlled manner because if it is not
controlled this acetaldehyde will be
undergoing further oxidation and that
will be getting converted to a carboxyl
acid understood that's why it has to be
removed this has aldehyde as soon as it
is formed it has to be removed from the
reaction mixture by distillation okay so
let us see how ketones are produced now
see these ketones are obtained by the
oxidation of secondary alcohols okay so
this is a secondary alcohol this is a
isopropyl alcohol understood
isopropyl alcohol
isopropyl alcohol so this is a secondary
alcohol so when this secondary alcohol
when it undergoes oxidation in the
presence of acidified potassium
dichromate we get a ketone okay here
also the hydrogen from this carbon and
this hydrogen will be getting removed as
water molecule and finally we will be
getting a ketone ch3
c
double bond o
ch3 okay this is acetone or dimethyl
ketone plus water molecule okay so this
is acetone acetone or next we shall see
how this aldehydes and ketones can be
prepared by reductive ozonolysis of
alkenes okay see here this aldehydes can
be obtained by the reductive ozonolysis
of alkanes which do not possess
branching which do not process branching
at the carbon atoms
which which are involved in this double
bond okay these two carbon atoms are
involved in the double bond okay and
this should not have branching okay
those type of
alkenes can produce aldehydes okay now i
am taking a unsymmetrical alkene what am
i unsymmetrical i can see here this is a
double bond and this carbon this is
another carbon and here this side is not
same as that of this side so this is
unsymmetrical uh
alkene okay when we are making use of
unsymmetrical alkene and this
unsymmetrical alkene will be undergoing
oceanolysis and finally we will be
getting two types of aldehydes but when
we are making use of symmetrical alkenes
we will be getting the same type of
aldehyde so now let us see how this
works out okay i have taken propylene
methane
and propane so it's a double bond so
propylene this propylene the first
reacts with ozone okay
and it forms a intermediate product so
what happens how this ozone it uh
combines c h
o
c h two
here one o
o
o okay so now
this is called as propylene this is
called as
propylene
ozonoid
propylene ozonoid understood now this
propylene ozonite then it reacts with a
zinc dust okay in the presence of water
and there will be a what what what
happens here oceanologist takes place
okay see here
what happens when it is treated with
zinc test this oxygen right see this
oxygen will combine with zinc and that
will be removed as
zinc oxide okay minus zinc oxide and
finally you will be getting acetola ch3
cho acetolian
h2co mean hcho that is formaldehyde so
two types of products you are getting
acetaldehyde ch3 ch o plus formaldehyde
h c h o so since we are making use of
unsymmetrical alkene we are getting two
different aldehydes if you are making
use of same alkene uh same sorry
symmetrical alkane then you will be
getting same type of altitudes
understood now we shall see how ketones
are produced see ketones are obtained by
the reductive oceanologist of those
alkenes which possesses branching okay
at one carbon or both the carbon atoms
which are involved in double bond
understood so if if the carbon atoms
which are involved in double bond are
having branches then it will be giving
those type of alkenes will be giving
ketones understood so i have taken 2 3
dimethyl but 2 in okay so methane ethane
propane butane and it's having a double
bond in the second carbon so two in and
two methyl groups are there in second
and the third position so two three
dimethyl but two in understood so let us
see how this undergoes also analysis
first it will become this uh alkene will
be combining with ozone to form an
intermediate compound okay so let me
write the compound now
ch3
c
ch3
now there will be a link here oxygen
then again carbon right then here ch3
ch3
oh
just like the previous one we are
getting okay then again this will react
with the sink dust in the presence of
water and again there will be ozonolysis
okay here
here there will be a break and this
oxygen will combine with zinc to form
zinc oxide so minus z10 o and you will
be getting two molecules of acetone ch3
then c double bond o ch3 so you'll be
getting two dimethyl ketones two
molecules of dimethyl ketone or acid
next we shall see how these allots and
ketones are prepared from alkynes that
are triple bonded compounds okay so
aldehydes and ketones can also be
prepared by the hydration of alkynes
okay see here i'm taking acetylene first
for the preparation of aldehydes okay
when this acetylene is passed through
dilute sulfuric acid in the presence of
one percentage of mercuric sulfate at
333 kelvin see that the temperature is
333 kelvin if this acetylene it
undergoes hydration to give acetaldehyde
okay so we'll be getting acetaldehyde
ch3ch
oh right but before the formation of
this acetaldehyde will be getting an
intermediate product okay how how this
intermediacy this water molecule it
splits as h plus
and o h minus okay now this h plus will
be getting attached to this carbon and
this oh will be getting attached to this
carbon and we'll be getting a and
getting an unstable intermediate okay so
what could be the unstable intermediate
c h 2 double bond c h o h okay so this
compound is called as
vinyl alcohol vinyl vinyl alcohol and it
is highly unstable okay so since it is
very unstable immediately it transforms
to acetaldehyde
ch3cho understood students this is how
we shall we will be preparing aldehydes
now we shall take into account the
ketone so how these ketones are prepared
actually instead of acetylene if you are
making use of
other type of
alkynes we'll be getting ketones okay so
instead of acetylene alone will not give
ketone other all the other alkynes will
be giving ketones so i have taken
propane okay methane
when this propane uh is passed to dilute
sulfuric acid in the presence of one
percentage mercuric sulphate will be
getting an unstable product just like
the previous one see here this h2o will
be get splitted up into h plus or h
minus so what happens is this h plus
will be getting added up to this carbon
and this o h will be getting added to
this carbon understood so we'll be
getting the unstable product like this
ch3
single bond c h
c o h
then double bond ch2 okay this is an
unstable intermediate now this will be
since it is unstable immediately it will
be getting transformed to a ketone ch3 c
double bond o ch3 so this is acetone or
dimethyl ketone understood this is how
we'll be preparing
okay next we shall see how this
aldehydes and ketones are produced from
acid chlorides okay see this aldehydes
and ketones can be obtained by the
catalytic hydrogenation of acid chloride
so first let us see how this aldehydes
are produced see actually this in this
method hydrogen gas is passed through a
solution of uh acetyl chloride so i am
taking acetyl chloride as an example so
hydrogen gas is passed through this
acetyl chloride in boiling styling okay
in the presence of palladium catalyst
supported over barium sulfate okay so
palladium catalyst taken in in the
presence of in uh which is supported by
barium sulfate and partially poisoned
with sulphur okay or quinoline so this
process is called as rose and means
reduction so now acetyl chloride i have
taken so hydrogen is passed through this
acetyl chloride the presence of
palladium catalyst supported by barium
sulphate in boiling silent and if this
palladium catalyst is partially poisoned
by sulphur okay so what happens is uh
here we get uh acetaldehyde c h3 cho
plus hcl okay we'll get hcl so this is
what happening right now
why we are making use of this uh poison
sulphur see if this catalyst is not
poison the allocate formed in this
reaction will easily get reduced into
alcohol okay alligator will be further
reduced to alcohol and we'll get an
alcohol instead of algae okay so that's
why we are making use of a poison so
that we can hinder the reaction as soon
as we are getting this
should be removed immediately okay next
comes this ketones actually as i told
you earlier this alternate this process
is otherwise called as rose sentiment
reduction but now this ketones cannot be
obtained by this rose and
okay but it can be prepared easily by
treating this acetyl chloride with dye
methyl cadmium c2 methyl groups are here
so dimethyl cadmium in the presence of
dry ether when this acetylene turret is
treated with dimethyl cadmium in the
presence of dry heater we get as a tone
okay so ch3
c
double bond o
sequence 3 understood so this is what we
are getting acetone
plus cadmium chloride cdcl2
okay so now
next we shall see how this alligates and
ketones are produced from carboxylic
acids actually by dry distillation of
calcium salts or carboxylic acids we can
easily produce aldehydes and ketones
okay first we shall see how aldi gates
are produced see this aldehydes are
obtained when a mixture of calcium salt
of a carboxylic acid here i have taken
uh acetic acid okay so calcium salt of
this acetic acid is treated with calcium
formate okay calcium salt of formic acid
right so now when these two are
subjected to dry distillation it's
possible to get acetaldehyde okay so
this is calcium acetate and how how
there will be removal of two okay like
here also c
c
all right so we'll be getting
acetaldehyde two molecules of acetate
ch3cho
okay plus calcium carbonate all right so
this is how we are preparing
acetaldehyde from calcium acetate and
calcium forming next we shall see how to
prepare ketones okay see ketones can be
obtained by the dry distillation of
calcium salt of carboxylic acid again so
i've taken acetic acid so calcium salt
of this uh
acetic acid that is calcium acetate when
it is undergoing dry distillation it
produces ketone okay so how it's formed
c h3
ch3
c double point o just like the previous
one here also there will be a removal of
calcium carbonate
finally we shall see how this
all gates are produced from the nitrous
okay this preparation is otherwise
called a stiffens reduction what happens
in stiffness reduction is the partial
reduction of a cyanide into an amine
chloride by zinc standard chloride and
hcl at chrome temperature is called
stiffness reduction okay so the immune
hydrochloride on boiling with water gets
catalyzed to get aldehyde okay so let me
take an example methyl sine cyanides are
nitrile okay in a cs3c triple bond and
when it is undergoing reduction okay in
the presence of hcl at uh 290 to 295
kelvin in the presence of ether this
methyl cyanide will be getting converted
to acid acetyl domain okay acetone you
mean hydrochloride ch3 so it's an adduct
ch3 ch
double bond nh
hcl okay so this this gets
get added up to the methyl cyanide and
finally we are getting an uh adduct and
this is called as
epa
acetyl dimin acetyl the mean
hydrochloride okay hydrochloride
this again
uh when it is boiled with water when it
is boiled with water we get acetaldehyde
cho
plus ammonium chloride again h4
okay this is how we are preparing
acetaldehy or aldehyde from the nitrous
buds difference reduction understood
you might have understood all the
preparation of allocates and ketones in
this session i shall meet you with
another important topic in a short
period until then it's santera signing
off from me thanks for watching
you
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