Terephthalic acid
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2008-06-22T19:04:20Z
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{{Chembox new
| Name = Terephthalic acid
| ImageFile = Terephthalic-acid-2D-skeletal.png
| ImageName = Terephthalic acid
| OtherNames = Benzene-1,4-dicarboxylic acid<br />''para''-Phthalic acid<br />TPA<br />PTA
| Section1 = {{Chembox Identifiers
| SMILES = C1=CC(=CC=C1C<br />(=O)O)C(=O)O
| CASNo = 100-21-0
| RTECS = WZ0875000
}}
| Section2 = {{Chembox Properties
| Formula = C<sub>6</sub>H<sub>4</sub>(COOH)<sub>2</sub>
| MolarMass = 166.13 g/mol
| Appearance = white crystals or powder
| Density = 1.522 g/cm³
| Solubility = 0.0017g in 100g H<sub>2</sub>O at 25°C
| SolubleOther = Soluble in [[Dimethyl sulfoxide]], [[Dimethylformamide|DMF]], and alkalies. Slightly soluble in [[ethanol]], [[methanol]], [[formic acid]] and [[sulfuric acid]]. <ref>Sheehan, R.J. Terephthalic acid, dimethyl phthalate and isophthalic acid. In: Ullmann's encyclopedia of industrial chemistry. 5th completely revised ed. Vol. A 26. VCH Verlagsgesellschaft, 1995. p. 193-204</ref>
| MeltingPt = 427°C in a sealed tube
| Melting_notes = sublimes at 402°C (675 K) in air
| BoilingPt = sublimes
| TriplePoint = 427°
| pKa1=3.54 at 25°C </br>
pKa2=4.46 at 25°C <ref>[http://www.intox.org/databank/documents/chemical/terephac/cie474.htm CHEMINFO: Terephthalic acid<!-- Bot generated title -->]</ref>
}}
| Section3 = {{Chembox Structure
| CrystalStruct =
| Dipole = zero
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS =
| EUClass = not listed
| FlashPt =
}}
| Section8 = {{Chembox Related
| Function = [[carboxylic acid]]s
| OtherFunctn = [[Phthalic acid]]<br /> [[Isophthalic acid]]<br /> [[Benzoic acid]]<br /> [[p-Toluic acid]]
| OtherCpds = [[p-Xylene]]<br /> [[Polyethylene terephthalate]]<br /> [[Dimethyl terephthalate]]
}}
}}
'''Terephthalic acid''' is one [[isomer]] of the three [[phthalic acids]]. It finds important use as a [[commodity]] [[chemical compound|chemical]], principally as a starting compound for the manufacture of [[polyester]] (specifically [[Polyethylene terephthalate|PET]]), used in clothing and to make plastic bottles. It is also known as '''1,4-benzenedicarboxylic acid''', and it has the chemical formula C<sub>6</sub>H<sub>4</sub>(COOH)<sub>2</sub>. It has recently become an important component in the development of [[metal-organic framework|hybrid framework]] materials.
==History==
Phthalic acid (the ortho isomer of terephthalic acid) was obtained by [[France|French]] [[chemist]] [[Auguste Laurent]] in [[1836]] by [[oxidation|oxidizing]] [[naphthalene]] tetra[[chloride]], and, believing the resulting substance to be a naphthalene derivative, he named it naphthalenic acid. [[Switzerland|Swiss]] chemist [[Jean Charles Galissard de Marignac]] determined its formula and showed Laurent’s supposition to be incorrect, upon which Laurent gave it its present name, with teres meaning well-turned, refined, elegant in latin <ref>[http://www.archives.nd.edu/cgi-bin/lookup.pl?stem=teres Teres Definition]</ref> (symmetry increased over ortho and meta isomers).
==Properties==
It is almost insoluble in water, alcohol and ether; it sublimes rather than melting when heated. This insolubility makes it relatively awkward to work with, and up until around 1970 most crude terephthalic acid was converted to the dimethyl [[ester]] for purification.
==Production==
Terephthalic acid can be formed in the laboratory by oxidizing para-diderivatives of [[benzene]], or best by oxidizing [[caraway oil]], a mixture of [[cymene]] and [[cuminol]], with [[chromic acid]].
[[Image:Terephthalic-acid-chemical-synthesis.png|200px|Terephthalic-acid]]
On an industrial scale, terephthalic acid is produced, similar to [[benzoic acid]], by [[oxidation]] of ''p''-[[xylene]] by [[oxygen]] from [[air]]. This is done using [[acetic acid]] as [[solvent]], in the presence of a catalyst such as [[cobalt]]-[[manganese]], using a [[bromide]] promoter. The yield is close to 100%. The crude product is purified by [[hydrogenation]] while in a water solution to convert trace amounts of impurities to less harmful species. The solution is then cooled in a stepwise manner to [[crystallize]] out a highly pure terephthalic acid. Over 90% of the terephalate feedstock for the polyester industry uses this process, and all plants built within the last few decades are of this technology. Alternatively, but not commercially, it can be made, via the '''Henkel process''' (company) also known as '''Raecke process''' (patent holder), which involves the rearrangement of [[phthalic acid]] to terephthalic acid via the corresponding potassium [[salt]]s.<ref>{{cite journal
| title = The Preparation of Terephthalic Acid from Phthalic or Benzoic Acid
| author = Yoshiro Ogata, Masaru Tsuchida, Akihiko Muramoto
| journal = [[Journal of the American Chemical Society]]
| volume = 79
| issue = 22
| pages = 6005–6008
| year = 1957
| url =
| doi = 10.1021/ja01579a043 }}
</ref><ref>{{cite journal
| title = Further Studies on the Preparation of Terephthalic Acid from Phthalic or Benzoic Acid
| author = Yoshiro Ogata, Masaru Hojo, Masanobu Morikawa
| journal = [[Journal of Organic Chemistry]]
| volume = 25
| issue = 12
| pages = 2082–2087
| year = 1960
| url =
| doi = 10.1021/jo01082a003 }}
</ref> Terephthalic acid and [[dimethyl terephthalate]] are essentially all used as a [[monomer]] component in the production of [[polymer]]s, principally [[polyethylene terephthalate]] (polyester or PET). World production in 1970 was around 1.75 million tonnes.<sup>[2]</sup>. By 2006, global PTA demand had substantially exceeded 30 million tonnes.
==References==
{{Citationstyle|date=September 2007}}
<references/>
# [[1911 Encyclopedia]]
# ''Basic Organic Chemistry: Part 5, Industrial Products'', J.M. Tedder, A. Nechvatal, A.H. Tubb (editors), John Wiley & Sons, Chichester, UK (1975).
==External links==
*[http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc03/icsc0330.htm International Chemical Safety Card 0330]
*[http://physchem.ox.ac.uk/MSDS/TE/terephthalic_acid.html MSDS sheet]
[[Category:Dicarboxylic acids]]
[[Category:Monomers]]
[[Category:Benzoic acids]]
[[cs:Kyselina tereftalová]]
[[de:Terephthalsäure]]
[[fr:Acide téréphtalique]]
[[it:Acido tereftalico]]
[[nl:Tereftaalzuur]]
[[ja:テレフタル酸]]
[[no:Tereftalsyre]]
[[pl:Kwas tereftalowy]]
[[pt:Ácido tereftálico]]
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[[zh:对苯二甲酸]]