Naming & Drawing HydroCarbons - Carbon & its Compounds Video Lecture - Class 10

okay so continuing with last video that
we were looking at classifying alkane
hydrocarbons and actually going about
naming them and drawing them and we're
going to actually look at now what we
call the unsaturated hydrocarbons and
one in particular type book that we're
going to just focus on it are the
alkenes okay so there are other types of
unsaturated ones that it contains triple
bonds those are the alkynes
but we're just going to look at the ones
that contain these double bonds these
are called the alkene hydrocarbons
properties of alkanes alkenes are
unsaturated hydrocarbons they contain
double bonds only we looked at the
alkenes that's righti alkanes in the
last video and all the carbons had
single bonds between them these
unsaturated or and as we talked about in
previous lessons that the unsaturated
hydrocarbons contain double bonds maybe
even triple bonds but the ones we
actually look at actually contain double
bonds only so alkenes as opposed to
alkanes alkenes contain double bonds
only few other properties to know their
boiling point melting point are usually
slightly lower than those of alkanes
that have the same number of carbons
right so we have here three carbon atom
alright so we've got three carbons here
but if we look at its equivalent so we
look we're looking at something like
that might be propane and here something
that is propane right so notice here the
double bond so we're talking about their
boiling points melt and melting points
we're looking at it being lower okay
these ones are is lower than the alkane
Elementary with the same number of
carbons but different number of bonds
between them now also because of the
double bonds that are actually finding
in these alkenes right they are
considered much more reactive than
alkenes because of this presence of this
double bond alkenes are hydrocarbons
that contain one or more double bonds
within the main carbon chain so that's
one of that's the main difference
between the alkenes for this lesson and
alkanes from the last video okay and so
the same rules apply when looking at
name with the exception of when that
they have all the chains or the
hydrocarbons that we looked at last
class the last video the least number of
carbons that you have in in these
hydrocarbons is one carbon so we could
not have formed a double bond because
carbon has four valence electrons
hydrogen each has one valence electron
and does not have the ability to form a
double bond with any of these hydrogen's
so remembering is the one exception to
the rule so you won't really won't have
an alkene in there but if we look at
like ethane methane can become ethane
propane becomes propene okay pentane
becomes pentene okay now the name of the
compound ends in E and E that's the hint
right and that's the variation so the e
and e ending is found in these alkene
hydrocarbons so anytime you get that
ending eat any alkyne i'll show you i
like propane pentene right octene we're
looking at containing a double bond
within that carbon chain all the rules
for naming the compounds hold true
except for the fact that the double bond
takes precedence over all other branches
when you number
carbons in the chain so when you're
numbering the carbon right starting from
one two three
you always number the carbons starting
from the carbon closest to the double
bond okay we'll see that in one of the
examples here okay now we looked at a
mathematical formula with the alkanes
and we have another formula with the
alkenes so here we have cnh2n which
means if we have four carbons the
formula would be C 4 and then H 2 times
whatever that know the number of carbons
are which would be 4 leti so the formula
if we have four carbons would be c4h8
right this is the variation between the
now keying here and the alkane that we
looked at in the last video where with
CN h2 and that it was also 8 which
increased by two hydrogen's always
now rules to naming alkenes find the
longest continuous chain that contains
the double bond very very important
because if we're looking at it based on
the out Kane rules the longest chain
would be this one and five carbons but
in fact look at where the double bond is
so which means that it does not hold
true so for this example here the
longest chain we always want to look at
the double bond and so the longest chain
would be that because it includes this
double bond and when we're numbering
okay when we're numbering the other
dependents we always number eight
starting from the carbon that is closest
to the double bond which is that one two
three there are four curves so we know
based on the weeks based on the video
before I don't think of four carbons
right so we're not using the Greek
prefix we're using the whole monkeys eat
peeled bananas so bananas when you based
on the alkane was butane but because
this contains the double bond it's not a
butane it's a being team now the other
thing to keep in mind is where is the
location of the double bond and the
location of the double bond occurs
between the one and the two carbon so we
always number it based on the first two
lower than two networks right so it is
going to be eight one beauty because a
double bond which is represented with
the e on e is found on the first carbon
now let's look at the remaining branch
that actually comes off so we've gone a
two carbon branch that branches off here
from the second carbon on the beauty so
if it's on the second carbon based on
the other littles - remembering on -
separate members with letters so it's a
two and
Ethel so the name so we've got a -
enthalpy right we've got an ethyl group
found on the second carbon and a butene
fountain and with a double bond that is
found on the first carbon so we put this
together we write it as follows two FL
one G team okay so let's look at the
name here so we've got the two because
on the second carbon is where we found
the f OB the ethyl group contains two
cartons this one here tells us where the
double bond is and we know that we have
a double bond because the ending is e
and E all the hydrocarbons that end in E
and E have the double bond where is the
double bond located is shown with the
number in front notice as we said
numbers separating by letters we use
hyphens when separate numbers we use
commas we don't really have a comma the
need for a comma B there is no other
number you know so let's look at some
more of the rules here actually this
actually look at a first sample problem
using the rules and what we learned
let's look at the following compounds so
here we have the phone a compliment it's
easy to look at well look at the rules
the rules say let's look for the longest
chain of carbon atoms but this would be
the longest chain right if we were
naming alkanes but because we've got
this double bond this does not break
free so let's clear that
and now let's reorganize it and say well
you know one longest chain to include
the double bond is right there so as we
say to form now the next step is to
number them in accordance of the carbons
closest to the double bond carbon one
carbon two carbon three four carbon five
so we've got five carbons that have
this double bond so slice carbons
represents pentane but because it's
there's a double bond it's not pentane
it becomes ten teen now where is the
location of this double ball it's
located between carbon one and two so
remember as we said we number it based
on the lowest of the tube so it's a
1-pentene so now let's look at the
branches one we want here a couple of
branches or I'm sorry one branch we've
got the magic Euler and we've got a two
carbon branch right which is is
represented by an ethylene so it's a
Nephilim now what carbon is it located
it's located on the second carbon so
it's a tube ethyl 1-pentene right so to
telling us which carbon which carbon ism
is the double bond which carbon is the
ethyl group a part of okay and the main
chain is the pen team
let's name the following compound same
thing the same rules apply let's
identify the longest chain longest chain
right there and make sure we know that
we've got the double bonds and along
this chain that includes the double bond
so we've got one two three four five
carbons and again right five carbons
panting but because there's a double
bond it's no longer a pentane it's a
pentane now where is this double bond
located one let's number the carbons
starting from the one closest to the
double bond one two three four five
carbons so we've got five carbons the
location that double bonded between two
and three so the double bond other set
is based on the lowest of the two
numbers so it's a two
pantene and we look we've got another
branch located on the fourth carbon
right so we've got a four on the fourth
carbon what do we have we actually have
a methyl group so we have a on the form
carbon ribbon for methyl - two - pen
team so let's break this down double
bond on with a five carbon chain and
that double bond is located on the
second carbon we've got a methyl group
that is found on the fourth carbon of
this pentene main chain okay so
hopefully falling along
there's the the correct answer as we've
just gone let's look at something a
little bit more complicated so same
rules apply sickness now with this one
take a moment pause the video and
actually see if you can figure out the
answer of this one okay so hopefully
you'll have gotten the correct answer
now remember as we said when we try to
find the longest chain here's a double
bond right at this position right here
so we want to make sure that our chain
includes that double bond so we've gone
now let's number the carbons actually
before we number the carbons while we've
got how many garbage you've got one two
three four five six carbons so we've got
a hexane but because this contains a
double bond it's no longer a hexane
it's a x8 where is that hexene locally
well we've got one carbon two carbons
three carbons four carbons five six
carbons the double bond is located
between 2 & 3 right so it's a 2 hexene
that we've gone right so that's the main
chain 2 XE now let's look at the UM the
branched ones so we've gone an ethyl
group here 1 ethyl group we've gone
another ethyl group so we've got two
ethyl groups so we've got a dime ethyl
right we've got two ethyl groups one of
them had the 3 carbon another one I put
4 carbon so here's where the common lies
right between numbers now there's
another group that we have in here and
it's
here so we've got a one-carbon methyl
group another carpet methyl so we've got
two methyl groups so we've gone a dime
[Music]
methyl where is the dimethyl group
located it's located on the two carbon
and it's located on the five carbon so
we've got a two five dimethyl a three
four diethyl and we've got the two XE so
how do we go about me well the last part
right right the root of the name of the
hydrocarbon will always be whatever the
main chain is now we've got to figure
out which one of these is it this one or
is it this one that we're writing first
and for those who remember from the last
video we always put it based on the
alphabetical order of the actual carbon
chain so we're not looking at it as this
with this prefix dying we're looking at
it as well we've got a methyl group and
we've got an ethyl group so which one of
those alphabetically comes in first and
obviously the ethyl group
so when naming this we are going to put
this in the following order
it's a 3/4 die ethyl
-
two-five dimethyl i'm sorry for the mess
- then we put the two - hexene so let's
let me show it to you a little bit
simpler here okay so we've got the three
four die ethyl so we've got two ethyl
groups located on the three and the four
carbon of our main chain we've got two
methyl groups on the number two carbon
and the number five carbon of our main
chain our main chain ends in E and E so
it means we've got a double bond where
is that double bond located it's located
on carbon number two of this main chain
okay so hopefully that helps you out
you'll be able to go about naming any
one of these types of alkenes now
drawing out keys be careful to ensure
that each carbon only has four bonds
associated with it count your bonds very
carefully now only did the only
difference in drawing these alkenes is
to remember to place the double bond in
the main chain right so you always want
to have the main chain but again as you
said the most important thing to be
careful remember carbon bonds only four
bonds associating you know you'll
understand what I mean by this one now
we'll be actually drawing it up and when
the does that play a role this plays a
role when we're adding our hydrogen's to
each one of the carbons at the end once
we've drawn our our condensed structural
diagram of
alkane so let's look at them practice
problem draw a condensed structural
diagram for the compound two methyl 1
butene so first thing let's find the
maintain beauty so based on I guess
butane with a double bond we know
monkeys eat peeled bananas for carbons 1
2 3 4 now you have the choice to number
them anywhere you want I like to number
them in the order of strong left to
right 1 2 3 4 so we know we've got a 1
beauty right so which means we've gone
this one this double bond located on the
number one carbon so it's between 1 & 2
so I've drawn in now my butene so then I
can just drawing my single bonds two to
the cargo next I'm going to draw my
methyl group on the second carbon so
here's my second carbon I'm going to
drop my methyl group which is ch3 to the
other ends so I've got my double bond
between the 1 & 2 right to represent the
beauty number 4 carbons because the
chain is a butane derivative but because
there's a double bond it's a butene on
the 1-butene we've got our methyl group
on our second carbon now we have to fill
in our hydrogens now here's where we
said to be careful with look at this
carbon here it's already got a double
bond to this next carbon which means
it's got room for two more hydrogen's
however we said usually at the ends
we're able to put the ch3 right but it
doesn't work with the double bond right
even though the double bond is to the
outlook because a double bond is to the
outside it doesn't apply to this rule
right with the alkene so it's really
important to be careful now let's look
at this next carbon
this next carbon has a single bond to
this carbon a double bond to that carbon
and a single bond to that carbon it has
no more room to add any hydrogen so we
cannot add any more hydrogens this next
carbon carbon number three has single
bonds on either end which means it has
room for two more hydrogen's last one is
the outer end this carbon is bonded once
so it has room for three more hydrogen's
so here is the following formula for two
methyl one beauty it so be really
careful when you're drawing in your
hydrogen's okay and this is what we call
a condensed structural diagram and let's
look at the last sample problem a little
bit more challenging so dry condensed
structural diagram for the compound five
ethyl three four six tri methyl two
octane so take a moment and actually
work this one out think of the rules
that we talked about as to where to
start and see if you get the right
answer so first things first always
start from the main chain octene okay so
we've got an octane derivative of octane
so there are eight carbons one two three
four five six seven eight
so let's number them one two three four
five six seven eight cards now we've got
the the octane right so far it's an
octane we haven't put in two double
bonds we need to put where we put the
double bond
that number in front of the main chain
on team tells us where this double bond
is located it's located on the second
carbon but remember because it's on this
second carbon right here right if I put
it here it's between the 1 & 2 so that's
really the first card we're basing it
from between the 2 and the 3 so that's
where our double bond will over her so
now I can just put single bonds for all
the remaining carbon so I put in my
double bond really important now we've
got a 5 equal group so a 2 carpet branch
on the fifth carbon so I'm going to draw
underneath so here's one carbon here's
another card remember as we said carbons
at the ends if they're single bonds are
bonded to three hydrogen's if they're in
the middle with two with a single bond
on either end of the carbon there is
only two hydrogen's so now we've done
the fly methyl group so now we've got
three metals found on these three four
and six carbon so I'm going to draw them
above so one methyl group on the 3
another methyl group on the 4 and
another methyl group here on the sixth
carbon so now what's left drawing in my
hydrogen's so I'm putting my hydrogen's
remember as we said usually at the outer
ends they are H they're three H's
because it's a single bond right here
same color single bond here we have room
to put three hydrogen's because that
carbon is only bonded once now this
carbon here the number two carbon has a
double bond and a single bond which
means it
as room for one more hydrogen okay sorry
about the mess now this next carbon
carbon number three has a double bond on
one side and a single bond and branch to
a methane it's got four bonds
surrounding it there is no more room for
carbons next carbon carbon number four
has single bonds to those carbons with a
single bond to the branch so it has room
for one more
hydrogen next one three bonds has room
for one more hydrogen next one three
bonds it has room for for one more
hydrogen next one has two bonds right so
it has room for two hydrogen's and the
last part since it's bonded only once
has room for three hydrogen's so here is
although a rather messy example of a
condensed structural diagram for a five
ethyl three four six tri methyl two
octene okay so to break this down if you
want to double-check it well here's our
main chain it's an opportunity there are
eight carbons that contain a double bond
it contains a double bond on the second
carbon
alright so it's second between second
and third then we put in our three or
four or six tri methyl three methyl
groups one on the 3 the 4 and the 6 and
then do we have the ethyl on the fifth
carbon yes we do and there it is
so hopefully as I said with the last
video the key to understanding this is
practice practice practice there are
several websites online that you can go
is type in naming and drawing alkanes or
jeans and there are various websites
that will give you the practice so it
will give you an example you give the
answer it will tell you if it's right or
wrong and then give you the correct
answer so do a Google search of naming
alkanes naming out teams to do this
practice because you need the practice
okay