Under certain circumstances it is necessary to indicate in the name of a ring, or ring system, containing the maximum number of non-
cumulative double bonds, one or more positions where no multiple bond is attached. This is done by specifying the presence of an '
extra' hydrogen atom at such positions by citation of the appropriate numbered locant followed by an italicized capital
H. Example:
A second type of indicated hydrogen (sometimes referred to as '
added hydrogen') describes hydrogen atoms added to a specific structure as a consequence of the addition of a suffix or a prefix describing a structural modification. This type of indicated hydrogen is normally cited in parentheses after the locant of the additional feature. Example:
Source:
InChI=1/C4H5N/c1-2-4-5-3-1/h1,3-4H,2H2
VXIKDBJPBRMXBP-UHFFFAOYAS
InChI=1/C5H5P/c1-2-4-6-5-3-1/h1-5H
UNQNIRQQBJCMQR-UHFFFAOYAZ
InChI=1/C5H5OP/c6-5-3-1-2-4-7-5/h1-4,7H
ZULCYBOYDXQMTM-UHFFFAOYAP
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A.Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
doi:10.1351/goldbook.
