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Naming Cycloalkanes With Substituents, Cis & Trans, Bicyclo Alkane Nomenclature



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in this video we're going to focus on

naming cycloalkanes so let's begin with

this one here we have a three carbon

cyclo alkane you can see the three

carbons at the edges and we know that

three carbons is associated with the

name propane for an alkane so this is

called cyclopropane anytime you have a

ring of carbon atoms you need to add the

prefix cyclo so with that in mind what

is the name of this particular cyclo

alkane so here we have four carbons and

four carbons is associated with butane

so this is called cyclo butane

now there's two other common shapes that

you need to be familiar with this is

called cyclopentane since it's a ring

with five carbons and the one that looks

like a hexagon this is known as cyclo

hexane now go ahead and take a minute

and draw cyclo heptane and cyclooctane

so this is how you draw a cyclohexane

you can start by putting two lines

that's cyclo pectin and four cyclooctane

this is probably the most easiest way to

draw it it has eight sides and that's

how you draw cyclooctane

now let's say if we have a six carbon

ring with two carbons outside of it what

is the name of this particular cycle

alkane how can we name it so as a

substituent this group is known as an

ethyl group since it contains two

carbons keep in mind for one carbon it's

associated with the word methane as a

substituent it's known as methyl ethyl

is two carbons propane 3 butane 4

pentane 5 hexane 6 heptane is for 7

octane is associated with 8 9 9 decane

10 to make sure you know the first 10

names of the common alkanes the name for

this compound is called ethyl

cyclohexane you just got to put these

two together and since you only have one

substituent you don't have to say 1

ethyl cyclohexane because it's

automatically on carbon 1 you need at

least 2 substituents to begin putting

numbers on it

what about this one how can we name this

particular alkane so this is a methyl

group since it only has one carbon and

here we have an ethyl group now when you

have multiple groups you want to put it

in alphabetical order e comes before M

so we want to put ethyl first before

methyl and if possible you want a number

in order and increase in order so we're

going to assign ethyl carbon 1 and

carbon 2 is going to be associated with

methyl we have five carbons in the ring

so we know it's a cyclopentane ring so

this is going to be called one ethyl -

two - methyl cyclo pentene you will

always need a - to separate a number and

a letter and if you have two numbers you

can separate them by a comma try this

one

go ahead and name this particular

compound by the way for each of these

examples feel free to pause the video as

you work on it so there's four carbon

atoms in the ring so the parent name is

called cyclo butane and we have a methyl

on carbon one and on carbon 3 so this is

going to be called 1 comma 3 use a comma

to separate the numbers - and dimethyl

since we have two methyl substituents

cyclo butane so that's the name for this

particular compound let's move on to our

next example

go ahead and name this compound so we

need to identify the longest chain the

longest chain is not the ring it is the

straight chain that we see here the ring

has six carbons but the chain above has

seven so that's going to be the parent

name which is associated with the word

heptane so what do we call this as a

substituent we know the parent name for

a six carbon ring is cyclohexane but as

a substituent is called cyclohexyl with

a yl so the name for this compound is

three cyclohexyl heptane

what is the name of that compound how

can we name it so we have a wedge and a

dash because one side is one chlorine

atom is in the front and the others in

the back this is the trans isomer and we

have a chlorine atom on carbon one and

two and the six carbon atoms in total in

a ring so we have a cyclohexane ring so

this is going to be called trance one

two dichloro

cyclohexane so if that's the case how

can we name this particular compound

since both bromine atoms are on the

wedge we have the sis isomer and we have

a total of five carbons in the ring so

this is going to be called sis one to

dye bromo cyclopentane

now what about this one

go ahead and name this particular cyclo

alkane so we have bromine group a bromo

group on carbon one and an ethyl group

on carbon three now because B comes

before E we want to put the one with the

B we want to say one bromo three advil

as opposed to one fo three bromo we need

to alphabetize it and if possible put it

in increase in order so to name it it's

going to be one bromo - three Ethel

cyclohexane so not only were we able to

put it in alphabetical order but we are

able to put the numbers in increase in

order which is preferable now let's move

on to by cyclic compounds

so let's say if we have a bicyclic

compound that is a compound with two

rings if it looks like that how can we

name it now the first thing you need to

be able to do is identify the bridgehead

carbons which are here now how many

carbons are between the bridgehead

carbons on the left side notice that we

only have two on the right side there's

only two carbons here and on top between

the two bridgehead carbons there's only

one so to name it it's going to be

called a bi cyclo into sin in order 2 to

1 and then add the total number of

carbons that we have which is going to

be the sum of these three numbers plus

the two bridgehead carbons which is 7 so

by Cyclone two-to-one heptane let's try

another example

go ahead and name this one so on the

left side there are two carbons on the

right side we have three and on top we

have one so to name it it's going to be

by cyclo 3 2 1 in descending order 3

plus 2 plus 1 is 6 and if you add the

two bridgehead carbons that's 8 + 8 is

associated with octane since we have a

total of 8 carbons so it's by cyclo 3 2

1

Achtung as you can see it's not very

difficult to name by cyclic compounds

but let's try one final example go ahead

and name this one notice that on the

left side we have two carbons we have

two on the right and in the top portion

between the two bridgehead carbons we

have two as well so this is going to be

called by cyclo 2 2 2 Achtung