Draw the structure for cis-2. 3-dibromo-2-hexene.

What is the IUPAC name for the molecule shown here

Draw the structure for cis-2,3-dibromo-2-hexene. Draw all
hydrogens explicitly.

Answer

General guidance

Concepts and reason
This problem is based on the concept of IUPAC nomenclature of alkenes.

IUPAC stands for international union of pure and applied chemistry. IUPAC has given a nomenclature to name the organic compounds. The IUPAC name consists of three parts: root name, prefix and suffix.

Fundamentals

The three parts of an IUPAC name are root name, prefix and suffix. The longest chain tells the root name. Prefix tells the position and name of the substitutions present on longest chain. Suffix tells the functional group present in the structure. Alkenes having same substituents at different sides across the double bond are called trans-alkenes and alkenes having same substituents on the same side are called cis-alkenes.

Step-by-step

Step 1 of 5

(1)

Structure of the compound is as follows:

There are two carbons present. Thus, the root for this compound is ‘eth’.

[Common mistake]

Count the carbon atoms carefully because number of carbon atoms decides the root name of the compound in IUPAC nomenclature.

Step 2 of 5

The structure of the compound with the numbering and prefix representation is as follows:

ū
ci
Trans

The same substituents of the olefinic carbons are present at the different sides across the double bond. Thus, the prefix will be ‘Trans’. Since both carbons have the same substituents, so numbering can be done be done from either side. Thus, the complete prefix will be ‘Trans-1,2’

Step 3 of 5

There are two chlorine atoms present. So, the name used for the substituents will be dichloro and since the compound is alkene. Thus, the suffix will be ‘ene’

The name of the compound is ‘Trans-1,2-dichloroethene’.

The compound contains two carbons. Thus, the root name will be ‘eth’. The same substituents of the olefinic carbons are present at the different sides across the double bond. Thus, the prefix will be ‘Trans’. Since both carbons have the same substituents, so numbering can be done be done from either side. Thus, the complete prefix will be ‘Trans-1,2’. There are two chlorine atoms present. So, the name used for the substituents will be dichloro and since the compound is alkene. Thus, the suffix will be ‘ene’. Thus, the name of the compound will be ‘Trans-1,2-dichloroethene’.

Step 4 of 5

2)

The name of the compound is cis-2,3-dibromo-2-hexene.

There are two bromine atoms attached in the cis configuration at the 2 and 3 position of a carbon chain that contains 6 carbon atoms.

Step 5 of 5

The structure of the compound is given below:

CH3
H₃C
CH2-CH2
Br
Br

The structure of cis-2,3-dibromo-2-hexene is as follows:

CH3
H₃C
CH2-CH2
Br
Br

There are two bromine atoms which are attached to the 2 and 3 position of the carbon chain that contains 6 carbon atoms and both the bromine substituents are in the cis configuration. Thus, the name of the compound is cis-2,3-dibromo-2-hexene. And above structure is correct structure of the compound.

Answer

The name of the compound is ‘Trans-1,2-dichloroethene’.

The structure of cis-2,3-dibromo-2-hexene is as follows:

CH3
H₃C
CH2-CH2
Br
Br

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