Talk:Maleic acid

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haha, can someone draw a diagram that looks less pixellated. i'll do it tomorrow if i don't forget

I read on the bottom of the page that something needed to be added, so I added that transformation from the cis-isomer to the trans-isomer in the classroom bit.

For common mortals, seeing this ingredient in the Saeco decalcifier, I did not find why it enters in the composition of a decalcifier. that would be cool to see. Thanks.

Maleate ion[edit]

The section on the maleate ion should be expanded. It should also include an image. The maleate ion has one less hydrogen on one of either of the two ends (since maleic acid is symmetrical, both hydrogens can dissociate equally well). Fuzzform 23:36, 31 October 2007 (UTC)[reply]

An obvious mistake[edit]

The boiling point is lower than the melting point. —Preceding unsigned comment added by 218.102.126.247 (talk) 11:08, 8 November 2007 (UTC)[reply]

That's only because of the decomposition. The compound isn't stable enough to retain its bonds when heated to that temperature range. So in essence, like many organic compounds, it has neither a melting nor boiling point (an intermolecular property) but only a decomposition point (an intramolecular property). —Preceding unsigned comment added by 137.30.93.201 (talk) 14:42, 10 September 2010 (UTC)[reply]

hi i'm doing a project on maleic acid and t learned alot —Preceding unsigned comment added by 71.192.147.92 (talk) 13:29, 6 October 2009 (UTC)[reply]

What is the charge on the maleate ion[edit]

Are both carboxyl groups ionised ? this book has "Maleate Ion HOOC-CH=CH-COO-" suggesting only one. If only one - is the one on the left or right as shown ? Why only one; Is there an internal hydrogen bond that prevents the second carboxyl from ionising ? - Rod57 (talk) 13:43, 14 September 2015 (UTC)[reply]

Depending on the situation, either one or both of the carboxylic acids can be deprotonated. Typically "maleate" refers to the ion with a single charge, and when it is a dianion it is referred to as "dibasic" as in this catalog listing: http://www.sigmaaldrich.com/catalog/product/sial/63260?lang=en -- Ed (Edgar181) 14:34, 14 September 2015 (UTC)[reply]

Toxicity of Maleic Acid, so it the Food reference in Error ?[edit]

I had been reviewing my old biochemistry text "Biochemistry, 8th edition (1970)" by James M. Orten and Otto W. Neuhaus, on page 266 where it discusses the Citric Acid Cycle, it makes the point that the trans isomer Fumaric acid is produced but the cis isomer Maleic acid is not produced and is "extremely toxic in the animal organism". The citation given is: Orten, J.M. and Smith, A.H.:Proc Soc. Exp. Biol. Med. 36:555, 1937. — Preceding unsigned comment added by 172.78.56.88 (talk) 23:01, 18 December 2016 (UTC)[reply]

Here is a NLM link on the toxicity of maleic acid: https://toxnet.nlm.nih.gov/cgi-bin/sis/search/a?dbs+hsdb:@term+@DOCNO+666 — Preceding unsigned comment added by 172.78.56.88 (talk) 23:07, 18 December 2016 (UTC)[reply]

The link you gave is no longer working, but maybe this helps:

https://pubchem.ncbi.nlm.nih.gov/compound/444266#section=Pharmacology

"9.3 Mechanism of Action

Maleic acid appears to affect Na+ and H+ ion transport in the proximal tubes [RE5]. After chronic exposure of male rats (250, 500, 750 mg/kg /per/ day for up to two years), an increased mortality as well as kidney damage and delayed growth was observed in all dosage groups. Liver and testicular damage has also been found in highest dosage group. No signs of carcinogenic activity of maleic acid were discovered with long-term dosage, which however was not designed as a carcinogenicity study".

So they tested much higher amounts (mg/kg) than people get from pharmaceutical drugs?

--ee1518 (talk) 16:28, 23 December 2020 (UTC)[reply]

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Natural occurencies?[edit]

Where is this acid found in nature?

There is a reference to the enzyme maleate isomerase used by bacteria for nicotinate metabolism in the text, but no section on if the acid form exists naturally somewhere or if there are important reactions for e.g. metabolism out there that the acid in involved in... Afro~svwiki (talk) 12:49, 10 August 2021 (UTC)[reply]