| Revision as of 18:06, 15 May 2011 edit63.232.109.71 (talk) →Popular culture← Previous edit |
Latest revision as of 18:52, 8 October 2024 edit undo81.154.157.184 (talk) →Chemistry |
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{{chembox |
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{{chembox |
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| verifiedrevid = 399520014 |
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| verifiedrevid = 429266344 |
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| Name = Ammonium thioglycolate |
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| Name = Ammonium thioglycolate |
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| ImageFile = Ammonium thioglycolate.png |
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| ImageFile = Ammonium thioglycolate.png |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey = ZZTCCAPMZLDHFM-UHFFFAOYSA-N |
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| StdInChIKey = ZZTCCAPMZLDHFM-UHFFFAOYSA-N |
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| CASNo_Ref = {{cascite|correct|??}} |
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| CASNo = 5421-46-5 |
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| CASNo = 5421-46-5 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = 6P9E788VZZ |
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| PubChem = 21534 |
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| Section2 = {{Chembox Properties |
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| Section2 = {{Chembox Properties |
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| Formula = NH<sub>4</sub><sup>+</sup>HSCH<sub>2</sub>COO<sup>−</sup> |
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| Formula = C<sub>2</sub>H<sub>7</sub>NO<sub>2</sub>S |
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| MolarMass = 109.15 g/mol |
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| MolarMass = 109.15 g/mol |
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'''Ammonium thioglycolate''', also known as '''perm salt''', is the chemical compound with the formula HSCH<sub>2</sub>CO<sub>2</sub>NH<sub>4</sub>. |
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'''Ammonium thioglycolate''', also known as '''perm salt''', is the ] of ] and ]. It has the formula HSCH<sub>2</sub>CO<sub>2</sub>NH<sub>4</sub> and has use in ] hair.<ref></ref> |
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==Chemistry== |
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Being the salt of a ] and weak base, ammonium thioglycolic acid exists in solution as an ] mixture of the salt itself as well as the free ] ] (HSCH<sub>2</sub>CO<sub>2</sub>H) and ]: |
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Being the salt of a ] and ], ammonium thioglycolate exists in solution as an ] mixture of the salt itself as well as thioglycolic acid and ammonia: |
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:HSCH<sub>2</sub>COO<sup>−</sup> + ] {{unicode|⇌}} ] + ] |
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:HSCH<sub>2</sub>COO<sup>−</sup> + {{chem2|NH4+|link=ammonium}} {{eqm}} ] + ] |
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Thioglycolate, in turn, is able to cleave ]s, capping one side with a hydrogen and forming a new disulfide with the other side: |
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==Chemical concepts related to perms== |
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:RSH + R′SSR′ ⇌ R′SH + RSSR′ |
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When discussing the chemistry of ], one should consider two chemical facts. First is the thiol-disulfide equilibrium: |
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===Use in perms=== |
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:RSH + R'SSR' {{unicode|⇌}} R'SH + RSSR' |
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A solution containing ammonium thioglycolate contains a lot of free ammonia, which swells ], rendering it permeable. The ] in the perm solution ] the disulfide ] bonds in the ] of the hair.<ref>{{Citation|title=Chemical and Physical Behavior of Human Hair, 4th ed|year=2000|pages=106–108|first1=Clarence R.|last1=Robbins}}</ref> In a sense, the thioglycolate removes crosslinks. After washing, the hair is treated with a mild solution of ], which oxidizes the ]s back to ]. These new chemical bonds impart the structural rigidity necessary for a successful perm. The rigidification process is akin to the ] of rubber, where commonly polysulfide linkages are used to crosslink the polymer chains. However, not as many disulfide bonds are reformed as there were before the permanent. As a result, the hair is weaker than before the permanent was applied and repeated applications over the same spot may eventually cause strand breakage. |
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Since polar molecules are less volatile than nonpolar ones, the glycolate substituent makes the thiol non-volatile and hence less odorous. An added advantage is that the glycolate confers some solubility in water. One could almost certainly use ] and ammonia to give a perm, but there would be serious olfactory consequences. |
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where R and R' are organic substituents such as methyl (-CH<sub>3</sub>), ethyl (-C<sub>2</sub>H<sub>5</sub>), or -CH<sub>2</sub>COO<sup>−</sup>. |
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==In popular culture== |
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The thiol-disulfide exchange reaction is accelerated by bases such as ammonia, because the base generates some ]ate anion (RS<sup>-</sup>), which attacks the disulfide. Thus the ammonia plays multiple roles (and more, see below) in this application. |
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In the 2001 film '']'', the protagonist, law student Elle Woods, wins her first case by proving that a witness who had gotten a perm the day of a murder could not have been in the shower at the time of the murder because "isn't the first cardinal rule of perm maintenance that you're forbidden to wet your hair for at least 24 hours after getting a perm at the risk of deactivating the ammonium thioglycolate?" (but mispronouncing it as "ammonium thyglockalate"). |
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The second chemical fact is that polar molecules are less volatile than nonpolar ones. So the glycolate substituent makes the thiol non-volatile and hence non-odorous. An added advantage is that the glycolate confers some solubility in water. One could almost certainly use HSCH<sub>3</sub> and ammonia to give a perm, but there would be serious olfactory consequences. |
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==The actual chemistry of perms== |
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A solution containing ammonium thioglycolate contains a lot of free ammonia, which swells ], rendering it permeable. The ] in the perm solution ] the disulfide ] bonds in the ] of the hair. In a sense, the thioglycolate removes crosslinks. After washing, the hair is treated with a mild solution of ], which oxidizes the ]s back to ]. These new chemical bonds impart the structural rigidity necessary for a successful perm. The rigidification process is akin to the ] of rubber, where commonly polysulfide linkages are used to crosslink the polymer chains. However, not as many disulfide bonds are reformed as there were before the permanent. As a result, the hair is weaker than before the permanent was applied and repeated applications over the same spot may eventually cause strand breakage. |
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==Popular culture== |
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In the 2001 film ], law student Elle Woods wins her first case by her knowledge of the chemistry of ammonium thioglycolate (which she pronounces "ammonium thyglocolate"), something she asserts "any ] girl would have known." |
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==References== |
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==References== |
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{{Unreferenced|date =September 2007}} |
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<references/> |
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<references/> |
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{{Ammonium salts}} |
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