Aldehydes, Ketones and Carboxylic Acid - Chemistry, Class 12 Video Lecture

Oh
mouth watering delights but they are not
just reading indulgences in fact they
are backbones of today's session in
chemistry don't believe me then why
don't I prove it to you in the studio
hi I am de Brito
your friend philosopher and guide to all
things chemical sweet aromas and flavors
hold coat in today's discussion on
compounds containing carbonyl group we
will begin with a general introduction
to what these compounds are we will
study the nature of the carbonyl group
we will move on to studying the
nomenclature of aldehydes ketones and
carboxylic acids the icing on our cake
will be the special exam tips we give
you in exam decoded so what exactly our
carbonyl groups they are functional
groups where the carbon atom shares a
double bond with oxygen it follows that
any compound that contains this group is
called a carbonyl compound many of these
compounds are used to impart aromas to
perfumes they are also used as flavoring
agents in food products this brings us
to the subject of what we saw in the
bakery you see I have a witness for
apple pie which contains cinnamon did
you know that the distinct taste and
aroma of cinnamon comes from a carbonyl
compound called three phenyl 2-propanol
it is commonly referred to as
cinnamaldehyde
if you noticed there was also vanilla
ice cream yes even vanilla contains the
carbonyl compound four hydroxy three
methoxy benzaldehyde with a much easier
to remember name vanilla
thus the flavour and aroma of both
cinnamon and vanilla is due to carbonyl
compounds known as cinnamaldehyde and
vanillin respectively
now that I have sweetened you up with
that information let's study a carbonyl
compound that is very different in both
nature and function you must be very
familiar with such sites by now
biological specimens that have been
protected from decay by a liquid
substance known as formally formally
reacts at a cellular level with living
tissue and prevents its breakdown
without it tissues break and the
specimen decays
time now to study the structure of these
fascinating groups of compounds but
first you need to understand a few
concepts the first is hybrid orbitals
orbitals which are formed by inter
mixing atomic orbitals are called hybrid
orbitals for example orbitals formed by
mixing an S orbital with two P orbitals
are called sp2 hybrid orbitals the
second important idea to understand is
Sigma and PI bonds Sigma bonds are bonds
formed by a head-on overlap of atomic
orbitals
while PI bonds are formed by sidewise
overlap of atomic orbitals coming back
to carbonyl compounds as I mentioned
before these groups contain carbon which
is double bonded with oxygen this
carbonyl carbon is sp2 hybridized this
means it has three sp2 hybrid orbitals
and one unhybridized p orbital it uses
sp2 hybrid orbitals to form three sigma
bonds which lie at an angle of 120
degrees the unhybridized p orbital of
carbonyl carbon overlaps with the p
orbital of oxygen to form a PI bond
we have already studied what a distinct
structure carbonyl compounds have let's
learn a bit more about it if we study
its molecular structure we observe that
the oxygen in the carbonyl group is more
electronegative than carbon therefore it
tends to attract the electron cloud
towards itself a partial negative charge
develops on oxygen and a partial
positive charge develops on carbon
thereby leading to the distinctive
polarity of the carbonyl group
this makes the carbonyl carbon
electrophilic and the carbonyl oxygen a
nucleophilic Center now as you may
recall nucleophiles are species that
attack positive center of an atom in
other molecules while electrophiles are
species that attack negative center of
an atom in other molecule
now that we are clear about the
structure of carbonyl compounds let's
study some of its types aldehydes and
ketones are the simplest carbonyl
compounds they both contain the same
carbon oxygen double bond but there is a
difference the difference is the
presence of a hydrogen atom attached to
the carbonyl group in aldehydes ketones
on the other hand don't have hydrogen in
aldehydes the carbonyl group has a
hydrogen atom attached to it together
with either a second hydrogen atom or
more commonly an alkyl or aryl Co you
can see the general formula on your
screens right now take a look at the
general formula for ketones where the
carbonyl group has two hydrocarbon
groups attached these can be either
alkyl or aryl groups
with that you have been introduced to
the simplest carbonyl compounds but
there is a lot more ahead so why don't
we take a short break
meanwhile try answering this name and
aldehyde which is used in the silvering
of mirrors see you on the other side of
the break with the answer