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Consider the following compound:

enter image description here

The name engraved below it is what ACD ChemSketch generated for me. However, my book mentions that "3-chlorotoluene" is the iupac name for this compound.

This is another compound:

enter image description here

My book mentions "2,4,6-trichlorotoluene" is the IUPAC name, while the above is the name generated by ChemSketch.

Now, I am confused as to which name to agree with.

Which name is correct?
Which IUPAC rule says that toluene (and other related siblings like phenol) should be/should not be a part of the IUPAC name?

NOTE: I know that even common names can be considered as PINs, but in my post I am dealing with systematic IUPAC name only.

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  • $\begingroup$ Phenol is different, though... 4-chlorophenol is OK. $\endgroup$ – orthocresol♦ Jan 7 '18 at 13:48
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    $\begingroup$ @orthocresol Is it preferred IUPAC or systematic IUPAC? $\endgroup$ – Gaurang Tandon Jan 7 '18 at 13:49
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    $\begingroup$ Yes, 4-chlorophenol is a PIN (P-63.1.1.1), whereas 4-chlorotoluene is not (explained in duplicate question). The reason is because phenol is designated as a preferred name which is substitutable at any position, whereas toluene is designated as a preferred name which cannot be substituted. $\endgroup$ – orthocresol♦ Jan 7 '18 at 13:50
  • $\begingroup$ @orthocresol Ok. And are non-toluene names, like the one generated by ACD above, always valid and are correct IUPAC names? $\endgroup$ – Gaurang Tandon Jan 7 '18 at 13:51