Chapter 5.5, Problem 5.42P

Interpretation Introduction

Interpretation:

The double bond present in the given compound is in cis or trans has to be determined.

Concept Introduction:

All the molecules have their unique names.  These names must be known in order to communicate.  But remembering all the chemical names is impossible as there are many numbers of molecules.  To avoid this, the IUPAC nomenclature of naming the molecules has to be understood.  By use of this the name of the molecules can be derived from the rules.  Every IUPAC name consist of five parts.  They are,

Stereoisomerism

Substituents

Parent

Unsaturation

Functional Group

Stereoisomerism indicate if the considered molecule has any stereocenters are present (R,S) and if double bond is present are cis/trans.  In order to name a double bond as cis/trans, the important condition is that, an identical group has to be present on either side of the double bond.  If the identical groups are present on the same side of double bond, then it is known as cis.  If the identical groups are present on the opposite side of the double bond then it is known as trans.

The groups that are connected to the main carbon chain is known as substituents.  The substituents are identified after the carbon chain is identified and the functional group present in the given compound also identified.  The substituents are named by adding “yl” to the end of the name which indicate that it is a substituent is an alkyl.  The $\text{OH}$ group is named as –hydroxy-, ${\text{NH}}_{\text{2}}$ group is named as –amino-, Ketone is named as –keto-, Aldehyde is named as –aldo- and Halogen is named as –halo-.  If there are more than one number of the same substituent, then the required prefix, di-, tri-, tetra- are added.

The longest carbon chain is known as the parent.  Parent carbon chain is the lengthiest carbon chain in the molecule that must include the functional group that is present in the compound.  The longest carbon chain is identified and the parent name is given by the number of carbon atoms that is present in it.  It must be remembered that even though functional group is not present in parent carbon chain, the double bond, triple bond if present has to be included.

Number of carbon atoms in chain	Parent
1	Meth
2	Eth
3	Prop
4	But
5	Pent
6	Hex

Unsaturation indicates that if any triple or double bonds are present in the molecule.  If a compound contains a double bond it is named as “-en-” and if a triple bond is present “-yn-” is used.  If a compound contains two double bonds, then it is named as “-dien-”.  If three double bonds are present in the given compound, then it is named as “-trien-”.  This same rule applies for the compound that contains multiple triple bonds also.

Functional group is the one after which the considered compound is being named.  Functional groups determine the chemical property of a compound.  While naming a compound using IUPAC nomenclature, we add suffix to the name of the compound to show what functional group is present in it.  Some of the examples are,

Functional Group	Class of compound	Suffix
	Ester	-oate
	Ketone	-one
	Aldehyde	-al
	Carboxylic acid	-oic acid
	Alcohol	-ol
	Amine	-amine