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There is no reaction of terephthalic acid heating effect on the internet (at least Wikipedia). I have written the most probable reaction possible as per my knowledge. Please tell if it is spontaneous and possible or not. Also, give real conditions of doing the reaction if possible.

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    $\begingroup$ It looks rather challenging to get those oxygens and hydroxies to face each other long enough for any dehydroxylation to happen. Like herding cats $\endgroup$ May 4 '21 at 7:24
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Following are the Statement from “On Terephthalic Acid and its derivatives” By Warren De la Rue and Hugo Muller February 7, 1861:

On heating, terephthalic acid sublimes without previously fusing(melting). The sublimate, which is indistinctly crystalline, has the same composition and properties as the original acid, and therefore, unlike other bibasic acids, terephthalic acid cannot be converted into an anhydrite by merely heating it

Terephthalic acid when pure is white opaque powder, insoluble in water and it sublimes at $\pu{300^{\circ}C}$ without melting. When heated to decomposition it emits acrid smoke and irritating fumes. $\ce{FeOOH}$, nickel hydroxide and nickel oxide are suitable catalyst for thermal decomposition of terephthalic acid (at low temperature) but since nickel compounds are expensive so $\ce{FeOOH}$ is generally used. At higher temperature (in absence of catalyst) Terephthalic acid$\ce{_{gas}}$ is decomposed to carbon dioxide,benzene and benzoic acid.

For further reading refer to this more in depth paper "Determination of the Thermal Decomposition Products of Terephthalic Acid by Using Curie-Point Pyrolyzer" by Mehmet uluturk

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  • $\begingroup$ +1 Thanks for the answer and welcome to Chem.SE. Please note that $\ce{...}$ is used to render chemical formulae and equations, as they are not supposed to be in italic. $\endgroup$
    – S R Maiti
    May 3 '21 at 20:56
  • $\begingroup$ @Jay Heating without catalyst, catalyst are only required at low temperature for this reaction. $\endgroup$
    – user1055
    May 4 '21 at 4:52
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@user1055 answered the question pretty much. I am just going to add a complementary answer which has the abstract to the paper which @user1055 mentioned. The abstract of the paper mentions the various products of the decomposition reaction:

The thermal decomposition behavior of terephthalic acid (TA) was investigated by thermogravimetry/differential thermal analysis (TG/DTA) and Curie-point pyrolysis. TG/DTA analysis showed that TA is sublimed at 276°C prior to decomposition. Pyrolysis studies were carried out at various temperatures ranging from 160 to 764°C. Decomposition products were analyzed and their structures were determined by gas chromatography–mass spectrometry (GC-MS). A total of 11 degradation products were identified at 764°C, whereas no peak was observed below 445°C. Benzene, benzoic acid, and 1,1′-biphenyl were identified as the major decomposition products, and other degradation products such as toluene, benzophenone, diphenylmethane, styrene, benzaldehyde, phenol, 9H-fluorene, and 9-phenyl 9H-fluorene were also detected. A pyrolysis mechanism was proposed based on the findings.

Reference

  1. A. Begüm Elmas Kimyonok & Mehmet Ulutürk (2016) Determination of the Thermal Decomposition Products of Terephthalic Acid by Using Curie-Point Pyrolyzer, Journal of Energetic Materials, 34:2, 113-122, DOI: 10.1080/07370652.2015.1005773
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