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indicated hydrogen

Also contains definition of: added hydrogen

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:
I03004-1
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:
I03004-2
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
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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.
Last update: 2014-02-24; version: 2.3.3.
DOI of this term: doi:10.1351/goldbook.I03004.
Original PDF version: http://www.iupac.org/goldbook/I03004.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.
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