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For some cyclic anhydrides, the -dioic anhydride suffix seems to be used. E.g. butanedioic anhydride (succinic anhydride). How does this apply to anhydrides which are not symmetrical about the oxygen atom bonded with two carbons?

Cyclic anhydride with 7 carbons and 1 double bond

Is it correct to call this compound "Hept-2-enedioic anhydride"?

According to ChemDraw online (JS Sample Page), its name is "(Z)-4,5-dihydro-2H-oxocine-2,8(3H)-dione". I don't understand this.

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    $\begingroup$ You could call it like that, but IUPAC has general nomenclature for heterocyclic compounds. Oxocine is parent unsaturated ether. $\endgroup$
    – Mithoron
    Commented Nov 14, 2023 at 15:38
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    $\begingroup$ Cyclic anhydrides are generally named as heterocyclic pseudoketones; see my answers here and here. $\endgroup$
    – Loong
    Commented Nov 14, 2023 at 17:38

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The current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) reads as follows:

P-65.7.7 Cyclic anhydrides

P-65.7.7.1 Cyclic anhydrides formed from two acid groups attached to the same parent hydride structure are named in two ways:

(1) as heterocyclic pseudoketones;

(2) by changing the class term ‘acid’ to ‘anhydride’ in the systematic or retained name of the dibasic acid.

Method (1) generates preferred IUPAC names

Using Method (1), the first step is naming the heterocyclic component. Heteromonocyclic rings with three through ten ring members having the maximum number of noncumulative double bonds (called mancude ring systems) are used as parent components. Since there is no retained name for the parent component of the compound that is given in the question, a systematic Hantzsch-Widman name is used, in this case oxocine.

The original parent structure oxocine ($\ce{C7H8O}$) has the maximum number of noncumulative double bonds for this kind of structure. Compared to an ideal unsaturated compound, however, oxocine has one extra hydrogen somewhere. The position of this extra hydrogen must be indicated. A few different isomers are possible; for example, the original parent structure could be 2H-oxocine.

2H-oxocine

The corresponding pseudoketone is named using the suffix ‘one’ in accordance with rules expressed for ketones, which gives the name (4Z,6Z)-2H-oxocine-2,8(3H)-dione.

(4Z,6Z)-2H-oxocine-2,8(3H)-dione

Finally, removing the extra double bond yields the complete name (6Z)-4,5-dihydro-2H-oxocine-2,8(3H)-dione.

(6Z)-4,5-dihydro-2H-oxocine-2,8(3H)-dione
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