4.3 IUPAC naming and formulae (ESCKG)

What is IUPAC naming? (ESCKH)

In stimulate to give compounds a name, particular rules need to be followed. Once naming essential compounds, the IUPAC (International Union of Pure and Applied Chemistry) nomenclature (naming scheme) is used. This is to provide consistency to the names. The also enables every link to have actually a distinctive name, which is not possible with the typical names offered (for instance in industry). Us will first look at some of the measures that must be complied with when naming a compound, and then try to apply these rules to some particular examples.

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A an excellent general dominion to follow is to begin at the end (the suffix) and work backwards (from best to left) in the name.


Molecules deserve to contain both dual or triple bonds and also other functional groups (e.g. One alkene and an alcohol functional team in one molecule - propenol). However, every molecules explored in this book will contain only solitary carbon-carbon bond when merged with other functional groups.


Number the carbons in the longest carbon chain (Important: If the molecule is not an alkane (i.e. Has actually a functional group) you should start number is numbered so the the functional group is ~ above the carbon with the lowest feasible number). Start with the carbon in ~ the finish closest to the practical group.

Look for any branched groups:

The branched teams must be listed before the surname of the main chain in alphabet order (ignoring di/tri/tetra).

If there are no branched teams this step can be ignored.


Number

prefix

2

di-

3

tri-

4

tetra-


Table 4.7: Prefixes because that multiple substituents with the same name. These use to multiple functional teams as well.


For the alkyl halides the halogen atom is cure in lot the same method as branched groups:

To name them take the surname of the halogen atom (e.g. Iodine) and replace the -ine through -o (e.g. Iodo).

Halogen

name

fluorine

fluoro

chlorine

chloro

bromine

bromo

iodine

iodo


Table 4.8: naming halogen atoms in essential molecules.


The halogen atoms should be listed before the name of the main chain in alphabetical order (ignore di/tri/tetra).

If there are no halogen atom this step deserve to be ignored.

Combine the aspects of the name right into a solitary word in the complying with order:

branched groups/halogen atom in alphabet order (ignoring prefixes) prefix of key chain name ending according come the sensible group and its position on the longest carbon chain. temp text

Naming hydrocarbons (ESCKJ)

naming alkanes

The suffix for an alkane is -ane.

Worked example 1: specify name the alkanes


Give the IUPAC surname for the complying with compound:

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Note: The number attached come the carbon atoms would certainly not typically be shown. The carbon atoms have actually been numbered to assist you to surname the compound.


Identify the useful group

The compound is a hydrocarbon with solitary bonds between the carbon atoms. That is an alkane and also will have actually a suffix the -ane.


Find the longest carbon chain

There are four carbon atom in the longest chain. The prefix of the compound will be but-.


Number the carbon atoms in the longest chain

The numbering has been done because that you here.


Look for any branched group, name them and give their place on the carbon chain

There are no branched teams in this compound.


Combine the elements of the name right into a single word

The surname of the link is butane.


Worked example 2: specify name the alkanes


Give the IUPAC surname for the adhering to compound:

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Identify the useful group

The compound is a hydrocarbon with solitary bonds in between the carbon atoms. That is one alkane and will have actually the suffix -ane.


Find the longest carbon chain

There space three carbon atom in the longest chain. The prefix because that this link is prop-.


Number the carbons in the carbon chain

If we begin at the carbon on the left, we have the right to number the atoms as displayed in red (left). If we start at the carbon top top the right, we deserve to number the atom as presented in blue (right).

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Look for any type of branched groups, name them and give their position on the carbon chain

There is a branched group attached come the second carbon atom. In this case the methyl team is top top carbon 2 nevertheless of which next you number the longest chain from.

This team has the formula ( extCH_3), i m sorry is methane without a hydrogen atom. However, since it is not part of the main chain, the is provided the suffix -yl (i.e. Methyl). The position of the methyl group comes just before its surname (see the following step).


Combine the aspects of the compound"s name into a single word in the order of branched group; prefix; name finishing according come the practical group

The compound"s name is 2-methylpropane.


Worked instance 3: naming the alkanes


Give the IUPAC name for the adhering to compound:

( extCH_3 extCH( extCH_3) extCH( extCH_3) extCH_3)

(Remember the the side groups are presented in base after the carbon atom to which they room attached).


Draw the structural formula indigenous its condensed structural formula

The structure formula of the compound is:

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Identify the functional group

The compound is a hydrocarbon with single bonds between the carbon atoms. It is an alkane and also will have actually the suffix -ane.


Find the longest carbon chain

There are four carbon atoms in the longest chain. The prefix for this compound is but-.


Number the carbons in the carbon chain

If we start at the carbon top top the left, we can number the atoms as displayed in red (left). If we begin at the carbon top top the right, we deserve to number the atoms as shown in blue (right).

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Look for any type of branched groups, surname them and give their position on the carbon chain

There are two methyl teams attached to the key chain. The very first one is attached to the 2nd carbon atom and also the second methyl team is attached to the 3rd carbon atom. An alert that in this example it does no matter just how you have actually chosen come number the carbons in the main chain; the methyl teams are quiet attached come the second and third carbon atoms and so the specify name of the compound is no affected.

This team will it is in 2,3-dimethyl-


Combine the elements of the compound"s name into a single word in the stimulate of branched groups; prefix; name ending according come the sensible group

The compound"s surname is 2,3-dimethylbutane.


Worked instance 4: naming the alkanes


Give the IUPAC name for the following compound:

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Identify the practical group

The compound is a hydrocarbon with solitary bonds in between the carbon atoms. That is one alkane and also will have the suffix -ane.


Find the longest carbon chain and also number the carbons in the longest chain

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There are 6 carbons in the longest chain if they are numbered as presented in red (on the left). There are only five carbon atom if they room numbered as displayed in blue (right). Therefore, the red numbering (on the left) is correct and also the prefix because that the link is hex-.


Look for any branched groups, name them and also give their position on the carbon chain

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There is one methyl team attached to the main chain. If us number as shown in red (on the left) the methyl is attached come the 4th carbon atom. If we number as displayed in blue (on the right) the methyl is attached come the third carbon atom.

After functional groups, the branched teams should have the lowest numbers possible. As such the blue number is numbered (on the right) is correct. The methyl is attached to the third carbon atom (3-methyl).


Combine the elements of the compound"s name into a single word in the order of branched groups; prefix; name finishing according come the useful group

The compound"s name is 3-methylhexane.


Worked example 5: specify name the alkanes


Draw the semi-structural structural and condensed structural formula because that the organic link 2,2,4-trimethylhexane


Identify the useful group

The name ends in -ane thus the link is one alkane.


Determine the number of carbon atom in the longest chain

The longest chain has the prefix hex-. There are because of this 6 carbon atoms in the longest chain.

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Look for any kind of branched groups and also place lock on the structure

The link is 2,2,4-trimethylhexane. As such there space three branched groups. 2 on carbon 2 and one top top carbon 4.

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Combine this information and include the hydrogen atom

Carbon atoms deserve to have four single bonds. Therefore wherever a carbon atom has less than four bonds attract in hydrogen atoms until there are four bonds.

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Condense the structure formula

First condensation the key chain: ( extCH_3 extCCH_2 extCHCH_2 extCH_3)

Then include the next chains (in brackets) top top the appropriate carbon atoms:

( extCH_3 extC( extCH_3)_2 extCH_2 extCH( extCH_3) extCH_2 extCH_3)


Naming alkanes


Textbook practice 4.8

Give the structural formula because that each of the adhering to alkanes


Octane


The suffix -ane tells united state that this is one alkane. The prefix oct- tells us that there are eight carbon atom in the longest chain.

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Propane


The suffix -ane tells united state that this is an alkane. The prefix prop- tells us that there room three carbon atom in the longest chain.

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2-methylpropane


The suffix -ane tells united state that this is an alkane. The prefix prop- tells united state that there are three carbon atom in the longest chain. 2-methyl tells united state that over there is a methyl (( extCH_3-)) branched team attached come the second carbon atom.

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3-ethylpentane


The suffix -ane tells united state that this is one alkane. The prefix pent- tells us that over there are 5 carbon atoms in the longest chain. 3-ethyl tells us that over there is an ethyl branched team (( extCH_3 extCH_2-)) team attached come the third carbon atom.

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Give the IUPAC name for each of the following alkanes:


( extCH_3 extCH_2 extCH( extCH_3) extCH_2 extCH_3)


This is difficult to perform unless you draw the structural formula the the molecule out. That is recommended the you execute this in exams.

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There are 5 carbons in the longest chain therefore the prefix is pent-. There space only solitary carbon-carbon bonds and no other functional team so the compound is one alkane and also the suffix is -ane. There is one methyl group at position 3 (you deserve to number native either end of the chain for this example). For this reason the link is 3-methylpentane.


( extCH_3 extCH( extCH_3) extCH_2 extCH( extCH_3) extCH_3)


This is difficult to perform unless you draw the structure formula of the molecule out. It is recommended that you carry out this in exams.

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There are 5 carbons in the longest chain, therefore the prefix is pent-. There are only solitary carbon-carbon bonds therefore the compound is an alkane and also the suffix is -ane. There is one methyl team at position 2 and one at place 4 (once again you can number from either end). For this reason the compound is

2,4-dimethylpentane.


( extCH_3 extCH_2 extCH_2 extCH_2 extCH_2 extCH_3)


This is tough to execute unless you draw the structure formula of the molecule out. It is recommended the you execute this in exams.

*

There are six carbon atom in the longest chain therefore the prefix is hex-. There room only solitary carbon-carbon bonds and no other functional team so the compound is one alkane and also the suffix is -ane. There space no branched groups, therefore the molecule is hexane.


( extCH_3 extCH_3)


This is difficult to do unless you attract the structural formula the the molecule out. That is recommended that you perform this in exams.

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There are two carbon atom in the longest chain so the prefix is eth-. There space only solitary carbon-carbon bonds and also no other functional group so the link is one alkane and also the suffix is -ane. There room no branched groups, so the molecule is ethane.


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There are four carbon atom in the longest chain, therefore the prefix is but-. There are two methyl branches at positions 2 and 3. The functional team is one alkane, so the suffix is -ane. Combining every this details we get: 2,3-dimethylbutane. Keep in mind that in this instance it does not matter which end you start numbering from.


*

There are 4 carbon atoms in the longest chain therefore the prefix is but-. The functional group is an alkane, therefore the suffix is -ane. There is one branched team which is a methyl group and this is at place 2. The molecule is 2-methylbutane.

Note the in this example it does matter which way you number the chain together the branched group needs to have actually the lowest number feasible and therefore the link is not 3-methylbutane.


naming alkenes

The suffix because that an alkene is -ene.

Worked example 6: specify name the alkenes


Give the IUPAC name for the following compound:

*

Identify the functional group

The compound has a double carbon-carbon bond and is an alkene. That will have actually the suffix -ene.


Find the longest carbon chain include the practical group

The functional group is a dual bond, for this reason the longest chain need to contain the double bond. Over there are four carbon atoms in the longest chain and also so the prefix because that this compound will certainly be but-.


Number the carbon atoms

Remember that the carbon atoms have to be numbered so that the functional team is in ~ the shortest numbered carbon atom possible. In this case, it doesn"t matter whether us number the carbons from the left to right, or indigenous the ideal to left. The twin bond will still fall between the 2nd and third carbon atoms.


Look for any type of branched groups, surname them and give their place on the carbon chain

There space no branched teams in this molecule.


Combine the aspects of the name right into a solitary word in the adhering to order: branched groups; prefix; name ending according to the useful group and its place along the longest carbon chain

The name of this compound is but-2-ene or 2-butene.


Worked example 7: naming the alkenes


Draw the structural and also molecular formula for the organic link

3-methylbut-1-ene


Identify the sensible group

The suffix -ene way that this link is an alkene and also there need to be a dual bond in the molecule. The number 1 automatically before the suffix method that the twin bond should be in ~ the first carbon in the chain (but-1-ene).


Determine the variety of carbon atom in the longest chain comprise the sensible group

The prefix because that the compound is but- for this reason there should be four carbons in the longest chain containing the double bond.

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Look for any kind of branched groups

There is a methyl group at the third carbon atom in the chain. Count from the left so the the twin bond carbon is the very first carbon atom.

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Combine this information and include the hydrogen atoms

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Reduce the structural formula come the molecular formula

There are 5 carbon atoms and 10 hydrogen atoms so the molecular formula is ( extC_5 extH_10).

(Remember the there is no structural information given by the molecule formula)


Worked instance 8: naming the alkenes


Give the IUPAC surname for the following compound:

*

Identify the sensible group

The link is one alkene and also will have the suffix -ene. There is a twin bond in between the first and second carbons and additionally between the third and 4th carbons. The organic compound because of this contains "1,3-diene".


Find the longest carbon chain containing the practical group, and number the carbon atoms

Remember that the main carbon chain should contain both the twin bonds. There are four carbon atoms in the longest chain containing the double bonds and so the prefix because that this compound will be but-. The carbon atom are currently numbered 1 come 4 in the diagram.


Look for any kind of branched groups, surname them and also give their place on the carbon chain

There is one ethyl team on the second carbon.

Note the if we had numbered indigenous the best to left the suffix would still have been 1,3-diene, but the ethyl team would have actually been on the 3rd carbon. For this reason we had to number left to right.


Combine the aspects of the name into a single word in the adhering to order: branched groups; prefix; name finishing according come the practical group and its position along the longest carbon chain

The name of this compound is 2-ethylbut-1,3-diene.


Naming alkenes


Textbook practice 4.9

Give the IUPAC surname for each of the following alkenes:


( extCH_2 extCHCH_2 extCH_2 extCH_3)


Draw the structural representation:

*

The molecule contains a twin carbon-carbon bond. It is one alkene and so the suffix is -ene. Over there are five carbons in the longest chain, so the prefix is pent-. There space no branched groups. The double bond occurs in between carbons 1 and also 2. So the molecule is 1-pentene or pent-1-ene.

Note that the means you number the carbon atoms matters here, the molecule is not pent-4-ene.


( extCH_3 extCHCHCH_3)


Draw the structure representation:

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The molecule includes a twin carbon-carbon bond. The is an alkene and also so the suffix is -ene. Over there are 4 carbons in the longest chain therefore the prefix is but-. There space no branched groups. The twin bond occurs between carbons 2 and also 3. The molecule is 2-butene or but-2-ene.


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The compound includes two twin carbon-carbon bonds. It is an alkene and so the suffix is -diene. Over there are 4 carbons in the longest chain comprise the dual bonds, therefore the prefix is but-. There are no branched chains. The first dual bond occurs in between carbons 1 and also 2. The second twin bond occurs between carbons 3 and also 4. The compound is but-1,3-diene.


Give the structural formula for each that the following alkenes:


ethene


The prefix eth- tells us there are two carbon atoms in the chain. The suffix -ene tells us there is a double bond between these carbon atoms.

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hex-1-ene


The prefix hex- tells united state there are 6 carbon atoms in the chain. The suffix -1-ene tells us there is a dual bond in between the first and 2nd carbon atoms.

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hept-3-ene


The prefix hept- tells us there are seven carbon atoms in the chain. The suffix -3-ene tells us there is a double bond between the third and 4th carbon atoms.

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4-ethyloct-3-ene


The prefix oct- tells us there are eight carbon atom in the longest chain containing the useful group. The suffix -3-ene tells united state there is a double bond between the third and 4th carbon atoms. 4-ethyl tells united state that there is one ethyl (( extCH_3 extCH_2-)) branched group attached come the fourth carbon atom.

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specify name alkynes

The suffix for an alkyne is -yne.

Worked example 9: specify name the alkynes


Give the IUPAC name for the following compound:

*

Identify the useful group

There is a triple bond in between two that the carbon atoms, so this compound is an alkyne. The suffix will be -yne.


Find the longest carbon chain include the practical group

The functional team is a triple bond, for this reason the longest chain should contain the triple bond. There are six carbon atoms in the longest chain. The prefix that the compound"s name will certainly be hex-.


Number the carbons in the longest chain

In this example, friend will have to number the carbons from appropriate to left so that the triple shortcut is in between carbon atoms with the lowest numbers (the suffix for the link will therefore be -2-yne).

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Look for any type of branched groups, name them and assign the number of the carbon atom come which the team is attached

There is a methyl (( extCH_3)) group attached to the fifth carbon (remember we have numbered the carbon atom from ideal to left).


Combine the elements of the name into a single word in the adhering to order: branched groups; prefix; name ending according to the functional group and its position along the longest carbon chain

If we follow this order, the surname of the link is 5-methylhex-2-yne.


Worked instance 10: naming the alkynes


Give the IUPAC surname for the following compound:

*

Identify the useful group

There room two triple bonds. The suffix will thus be -diyne.


Find the longest carbon chain comprise the sensible group

The functional team is a triple bond, so the longest chain need to contain all triple bonds. The longest carbon chain consists of seven carbon atoms, thus the prefix will certainly be hept-.


Number the carbons in the longest chain

*

Numbering from left to right (shown in red) the very first triple link is ~ above carbon 1 and also the 2nd is on carbon 5. The suffix will thus be -1,5-diyne.

(Numbering from best to left (shown in blue) will offer the suffix -2,6-diyne, and is incorrect).


Look for any kind of branched groups

There are no branched teams for this molecule.


Combine the facets of the name into a solitary word in the adhering to order: branched groups; prefix; name ending according come the sensible group and also its place along the longest carbon chain

The name of the link is hept-1,5-diyne.


Worked instance 11: specify name the alkynes


Draw the structural and condensed structural formula because that the essential compound

6-methylhept-3-yne


Identify the functional group

The suffix -3-yne means that this compound is an alkyne and there have to be a triple bond located on carbon number 3.


Determine the variety of carbon atoms in the longest chain include the practical group

The prefix because that the link is hept- for this reason there have to be seven carbons in the longest chain.

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Look for any branched groups

There is a methyl team located ~ above carbon number 6.

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Combine this details and add the hydrogen atoms

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Condense the structural formula

First condensation the main chain: ( extCH_3 extCH_2 extCCCH_2 extCHCH_3)

Then include the side chains (in brackets) ~ above the pertinent carbon atoms:

( extCH_3 extCH_2 extCCCH_2 extCH( extCH_3) extCH_3)


Naming alkynes


Textbook practice 4.10

Give the structure formula because that each the the following alkynes:


ethyne


The prefix eth- tells us there space two carbon atoms in the longest chain. The suffix -yne tells us there is a triple bond between the carbon atoms.

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pent-1-yne


The prefix pent- tells us there are five carbon atom in the longest chain. The suffix -1-yne tells united state there is a triple bond between the an initial and second carbon atoms.

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5-methylhept-3-yne


The prefix hept- tells us there are seven carbon atoms in the longest chain. The suffix -3-yne tells united state there is a triple bond between the third and fourth carbon atoms. 5-methyl tells us there is a methyl branched chain ~ above the 5th carbon atom.

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Give the IUPAC names because that the complying with alkynes:


*

There is a triple carbon-carbon bond. This link is an alkyne and will have actually the suffix -yne. Over there are 6 carbon atoms in the longest chain, thus the prefix will certainly be hex-. The triple link is in between the third and 4th carbon atom regardless of exactly how you number the chain (-3-yne). There are two branched methyl groups. Depending on the bespeak of number is numbered they room either on the 4th carbon atom (left to right) or the second carbon atom (right come left). The lower numbering is exactly (right to left) and as there space two methyl teams this is 2,2-dimethyl. The molecule is 2,2-dimethylhex-3-yne.


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There is a triple carbon-carbon bond. This compound is an alkyne and also will have actually the suffix -yne. There space three carbon atoms in the longest chain, therefore the prefix will certainly be prop-. The triple bond is between the first and second carbon atom (numbering indigenous the left) make the suffix -1-yne. There are no branched groups. This molecule is prop-1-yne or propyne.


( extCH_3 extCCCH_3)


Draw the structure:

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There is a triple carbon-carbon bond. This compound is an alkyne and will have the suffix -yne. There are 4 carbon atom in the longest chain, thus the prefix will certainly be but-. The triple shortcut is in between the 2nd and 3rd carbon atom regardless of how you number the chain (-2-yne). There are no branched groups. This molecule is but-2-yne or 2-butyne.


Model kits room a an excellent way to aid learners understand and visualise essential molecules. If you execute not have accessibility to version kits however, substitutes deserve to be used. A bag of jelly tots (or a comparable soft sweet) would work simply as well, using toothpicks to stand for the bonds. That is also feasible to make your very own playdough (which can be coloured for different atoms making use of food colourants). A recipe is provided here:

2 cups flour, 2 cups heat water, 1 cup salt, 2 tablespoons vegetables oil, 1 tablespoon of cream that tartar (this enhances elasticity, and also is optional).

Mix every the ingredients together over a short heat and also stir continually.

When the dough pulls away from the sides of the pot, eliminate it indigenous the warmth and permit to cool.

If your dough is still difficult just chef it a little bit longer.

Once cool, knead the dough until it becomes smooth, then different and include food colourant, various colours because that different varieties of atoms.

The dough is ready. Remember to save it in one airtight container between uses. If that dries the end a bit, knead in a little bit of water.

The full procedure is listed on www.instructables.com. This playdough deserve to be used for all the model building activities.

Be mindful to keep the playdough far from animals, together it is edible, however contains huge amounts the salt.

Building hydrocarbons

An instance of ethane, ethene and ethyne built with atomic version kits is provided in the picture below:

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Using atomic model kits, develop the molecules of methane, propane, butane, pentane and also octane. If you don"t have actually atomic model kits, jelly tots (or playdough) and also toothpicks will certainly work just as well. Usage one color jelly tot for the carbon atoms and one for the hydrogen atoms.

Remember the carbon atoms must have 4 bonds and also hydrogen atoms can have just one. You need to see the all this compounds have actually a similar formula, remember lock all have the basic formula ( extC_ extn extH_2 extn+2). What is the name of the homologous series that every these molecule belong to?

Build the molecule of prop-1-ene, but-1-ene, pent-1-ene and also oct-1-ene. Use 2 toothpicks to represent a double bond. You need to see that all these compounds have a comparable formula. Remember, castle all have actually the general formula ( extC_ extn extH_2 extn).

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try placing the dual bond at different positions within the molecule. Go this make any difference to the total number of carbon and hydrogen atoms in the molecule? What is the surname of the homologous collection that all these molecules belong to?

Build the molecule of prop-1-yne, but-1-yne, pent-1-yne and also oct-1-yne. Use three toothpicks to stand for a triple bond. You should see that all these compounds have actually a similar formula. Remember, they are all alkynes.

try placing the triple shortcut at different positions within the molecule. Go this make any type of difference to the total number of carbon and also hydrogen atoms in the molecule? What is the general formula for the alkynes?

Naming hydrocarbons