Editing Succinic acid (section)

==Physical properties==
Succinic acid is a white, odorless solid with a highly acidic taste.<ref name=Toxnet/> In an [[aqueous solution]], succinic acid readily [[ion]]izes to form its conjugate base, succinate ({{IPAc-en|ˈ|s|ʌ|k|s|ᵻ|n|eɪ|t}}). As a [[diprotic acid]], succinic acid undergoes two successive deprotonation reactions:
:(CH<sub>2</sub>)<sub>2</sub>(CO<sub>2</sub>H)<sub>2</sub>  →   (CH<sub>2</sub>)<sub>2</sub>(CO<sub>2</sub>H)(CO<sub>2</sub>)<sup>−</sup>  +  H<sup>+</sup>
:(CH<sub>2</sub>)<sub>2</sub>(CO<sub>2</sub>H)(CO<sub>2</sub>)<sup>−</sup> →   (CH<sub>2</sub>)<sub>2</sub>(CO<sub>2</sub>)<sub>2</sub><sup>2−</sup>  +  H<sup>+</sup>
The [[Acid dissociation constant|pK<sub>a</sub>]] of these processes are 4.3 and 5.6, respectively.  Both anions are colorless and can be isolated as the salts, e.g., Na(CH<sub>2</sub>)<sub>2</sub>(CO<sub>2</sub>H)(CO<sub>2</sub>) and Na<sub>2</sub>(CH<sub>2</sub>)<sub>2</sub>(CO<sub>2</sub>)<sub>2</sub>.  In living organisms, primarily succinate, not succinic acid, is found.<ref name=Toxnet>{{cite web|title=Succinic Acid|url=https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+791|publisher=Toxnet National Library of Medicine HSDB Database|access-date=28 May 2017|date=2005-01-31}}</ref>

As a [[radical (chemistry)|radical]] group it is called a succinyl ({{IPAc-en|ˈ|s|ʌ|k|s|ᵻ|n|əl}}) group.<ref>{{Cite web|url=https://www.merriam-webster.com/dictionary/succinyl|title=Definition of SUCCINYL|website=www.merriam-webster.com|access-date=2017-03-09}}</ref>

Like most simple mono- and dicarboxylic acids, it is not harmful but can be an irritant to skin and eyes.<ref name=Toxnet/>