971.2 - Derivatives of urea formed by replacement of hydrogen are named (a) as substitution products of urea or (b), if the substituent carries also a group to be cited as principal group, by use of the prefix "ureido-" for the group NH2-CO-NH-. If necessary, locants N and N' or 1 and 3, respectively, are added; the point of attachment of a ureido radical is denoted N or 1.
The following trivial names are retained for urea derivatives (numbered as shown) and may be associated with prefixes denoting substituents, derivatives being named in the usual way:
Examples to Rule C-971.2
or 1,1 -Diethylurea
(b) 2-(N'-Methylureido)-1-naphthoic acid
or 2-(3-Methylureido)-1-naphthoic acid
971.3 - The bivalent radical -NH-CO-NH- is named "ureylene" and is used in nomenclature for assemblies of identical units (see Subsection C-0.7) when the terminal nitrogen atoms are attached to radicals carrying the same group to be cited as a suffix, but it is not used for compounds in which the -NH-CO-NH- group forms part of a ring (for example, not for barbituric acid).
See Recommendations'93 Table 31(a)
Example to Rule C-971.3
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