Question

The structure of diglyme is $C{H_3}OC{H_2}C{H_2}OC{H_2}C{H_2}OC{H_3}$
Which of the following is the IUPAC name for diglyme
A. 2, 5, 8 trioxononane
B. bis(2-methoxy ethyl) ether
C. $\beta ,\beta '$-dimethoxy-diethyl ether
D. diethylene glycol dimethyl ether

Answer 1

Hint:In the IUPAC system ethers are named as alkoxy alkanes. The ethereal oxygen is taken with the smaller alkyl group and forms a part of the alkoxy group while the larger alkyl group is considered to be the part of the alkane.

Complete answer:
We know that the common names of ethers are derived by naming the two alkyl or aryl groups linked to the oxygen atom as separate words in alphabetical order and adding the word ether. In case of symmetrical ethers the prefix di is used before the name of the alkyl or the aryl group.
Therefore the above compound is an ether and ethers are classified as simple or symmetrical ethers if the two alkyl or aryl groups attached to the oxygen atom are the same and mixed or unsymmetrical ethers if the two groups are different.
We have been asked to find the IUPAC name of the above compound where its common name is stated as diglyme
\[C{H_3} - O - {C{H_2}}^2 - {C{H_2}}^1 - O - {C{H_2}}^1 - {C{H_2}}^2 - O - C{H_3}\] \[\]
Considering one of the –O- linkage let us number the attached chains to it for the nomenclature. We observe symmetrical ether that is two similar groups at the –O- linkage therefore we will use bis and the IUPAC name will be accordingly where lesser carbon chain is added with oxy, it is Bis(2-methoxy ethyl) ether.
Also it can be named as 2, 5, 8 trioxononane because we use oxo prefix to indicate that an oxygen atom replaces a $ - C{H_2}$ group and we relate the cyclic ether to the corresponding hydrocarbon ring. Therefore at position 2,5,8 –O- linkage changes into a $ - C{H_2}$ group counting from the right making it a nine carbon chain.

Therefore both option A and B are correct.

Note:
Ethers are relatively inert compounds also as inert as alkanes. Under ordinary conditions they are stable to bases, dilute acids and most other reducing agents. This is due to the fact that the functional group of ethers (-O-) does not contain any active site in their molecules compared to the hydroxyl groups of alcohols and phenols.