Is 3,5-diethyltoluene an accepted IUPAC name?

My book says that



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> Monocyclic substituted hydrocarbons are named as derivatives of benzene or compounds like cumene, toluene, xylene, etc. However, if the substituent introduced into such a compound is identical with the substituent already present in the compound, then the substituted compound is named as tge derivatives of benzene.
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But I guess that names like toluene have stayed due to historic reasons and are not accepted in IUPAC nomenclature. Is my book correct?




**Names like toluene are "[retained names](https://en.wikipedia.org/wiki/Retained_name)".**



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> In chemistry, a retained name is a name for a chemical compound that is recommended for use by a system of chemical nomenclature (for example, IUPAC nomenclature), but that is not fully systematic. - [Wikipedia](https://en.wikipedia.org/wiki/Retained_name)
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> ‘Retained names’ are traditional or common well-established names that may be used either as preferred IUPAC name or as an allowed alternatives in general nomenclature, for example, naphthalene, benzoic acid and pyridine. [IUPAC's Blue book, P-12.3](http://old.iupac.org/reports/provisional/abstract04/BB-prs310305/CompleteDraft.pdf)
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Later in the same draft, we read



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> Toluene, xylene and mesitylene are specific parent hydrides that are composed of two components, one cyclic and the other acyclic and saturated. These names are retained due to a long and well established tradition. Toluene and xylene are preferred IUPAC names, but are not substitutable; toluene is substitutable under certain conditions for general nomenclature. P-22.1.3
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> Furthermore, anisole and toluene **cannot be substituted by other
> methoxy or methyl groups**, respectively. P-46.2.3.2
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**Conclusion**:


* Names like toluene, anisole and xylene are **retained names**. They *are* preserved for historical reasons; however, their unsubstituted forms are PINs (Preferred IUPAC names).
* The name *3,5-diethyl toluene* isn't acceptable according to the systematic IUPAC nomenclature.
* If you want to name the compound below, it's called 1,3-diethyl-5-methylbenzene.
![](https://i.stack.imgur.com/HSyU5.gif)


[Source](http://www.pherobase.com/pherobase/gif/1,3-diethyl-5me-benzene.GIF)


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