Mancude

Various degrees and kinds of unsaturation are possible. Unsaturation may be cumulative (which means that there are at least three contiguous carbon atoms joined by double bonds, C=C=C) or non-cumulative (which is another arrangement of two or more double bonds, as in -C=C-C=C-). In nomenclature, unsaturated cyclic parent hydrides have, by convention, the maximum number of non-cumulative double bonds. They are generically referred to as mancudes — derived from the acronym MANCUD, the MAximum Number of non-CUmulative Double bonds. Four classes of cyclic parent hydride are therefore recognised ... 

For comparison, only a few dozen alkanes are designated as parent hydrides. Over 73 000 rings and ring systems are mancudes and about 10 000 are carbocycles. 

The extended Hantzsch-Widman system is used to name monocycles of saturated and mancude rings with between three and ten members, inclusive. The names are composed of two parts non-detachable prefix(es), indicating the heteroatom and a stem indicating the size of the ring. Names of prefixes (called a prefixes) are listed in Table 4.8 and names of stems in Table 4.9. 

Ring size Unsaturated (mancude) Saturated (mancude)... 

Fused polycyclic systems are very numerous and diverse. They are named using the structures and names of their smaller components and the concept of ortho-fusion, which is purely a formal operation encountered in nomenclature. This concept is essential to the naming of larger systems, and is the formation of one bond by the condensation of two bonds belonging to two different cyclic systems, one of them being a mancude ring. 

In one method, the non-detachable prefixes hydro- and dehydro- (in the case of mancudes only) can be used to indicate the addition or subtraction of one hydrogen atom. As even numbers of hydrogen atoms are involved when a carbon-carbon single bond becomes a double or triple bond, the multiplicative prefixes di-, tetra-, etc., as well as the appropriate locants, are used. The prefix dehydro- is always used to indicate the subtraction of hydrogen atoms from saturated heterocycles having Hantzsch-Widman names. 

The International Union of Pure and Applied Chemistry (IUPAC) produced a set of rules for the definition of highly complex ring systems. Under these guidelines a cyclophane (i) has a mancude ... 

The Hantzsch-Widman names are preferred for rings with up to 10 members, in organic nomenclature. For saturated rings and mancude rings (rings with the maximum number of... 

In this example, names (i) and (ii) need the additional octahydro prefix because the available parent hydrides for these constructions (triazatriborinine and naphthalene, respectively) are mancude (i.e. have the maximum number of non-cumulative double bonds). 

Ending resulting from the change of the ine ending in names of cyclic mancude ring systems to ino to form prefixes in fusion nomenclature. (See Section P-25.3 of the Blue Bookb.)... 

Although the majority of the ring systems considered in this section are fully saturated, a number conform to the mancude (maximum noncumulated double bond) structure, and some of these possess full cyclic conjugation and so merit consideration for the description aromatic. The... 

A cyclophane is a compound that has a MANCUDE ring system, that is to say, a MAximium number of NonCUmulative DoublE bonds, or assemblies of MANCUDE ring systems. 

Monocyclic polyenes containing the maximum number of non-cumulative double bonds (for short called mancude systems) and having the general composition C H or C H + i n> 6) can also be named as [n]annulenes. 

Heterocyclic compounds with up to ten ring members are generally named by the extended HW System. In order to do this, a hetero symbol (or several of these symbols) from the table of V terms (Table 4) is combined (eliding the final V ) with a stem term of the following Table 5 that indicates both ring size and degree of saturation. (Unsaturation here means maximum number of non-cumulative double bonds - mancude.)... 

The following scheme displays the (exceptional) numbering conventions that hold also for the fully unsaturated (mancude) basic skeleton, namely, 15H-cyclopenta[fl]phenan-threne. 

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