IHydroquinone

**I-Hydroquinone**, eyaziwa ngokuthi i-benzene-1,4-diol, noma i-quinol, iyisakhi esiphunga elimnandi eliyisikhombisa sengathi ilawuliwe wasebenzisa i-phenol, okuvela kubenzine, esinendlela yokuthi i-C6H4(OH)2. Iminyaka eminingi edlule, kwakucatshangelwa ukuthi imboni abanzi lama-hydroxyl enezindlu ezithathu zahlanganiswe ngendandatho ye-benzene kuqala phakathi. Iyinhlayiya eqinile emhlophe. Izakhiwe ezikhundleni zomzali wazo zibizwa ngokuthi ama-hydroquinones. Igama "hydroquinone" lasungulwa nguFriedrich Wöhler ngo-1843.
## Ukukhiqizwa
I-Hydroquinone ikhiqizwa ezimbonini ngezindlela ezimbili eziyinhloko.

* Indlela esetshenziswa kakhulu ifana nenqubo ye-cumene inqubo yokuxhumana futhi ihlanganisa i-dialkylation ye-benzene ne-propene ukunikeza i-1,4-diisopropylbenzene. Le ngxube ihlangana nomoya ukuze ithole i-bis(hydroperoxide), okufana ngokwakheka ne-cumene hydroperoxides futhi kuhlelwe kabusha nge-asidi ukunikeza i-acetone ne-hydroquinone.
* Umzila wesibili uhlanganisa i-hydroxylation ye-phenol phezu kwe-catalyst. Ukuguqulwa kusebenzisa i-hydrogen peroxide futhi kunikeza inhlanganisela ye-hydroquinone ne-ortho isomer yayo catechol (benzene-1,2-diol):
*: C6H5OH  +  H2O2  -> C6H4(OH)2  +  H2O

Ezinye izindlela ezingavamile zihlanganisa:

* Ukuhlanganiswa kwe-hydroquinone okuphawulekayo kusuka ku-acetylene ne-iron pentacarbonyl kuhlongozwa ukuthi i-iron pentacarbonyl isebenza njenge-catalyst, kunokuba ibe yi-reactant. Lapho kukhona igesi ye-carbon monoxide ekhululekile. I-rodium noma i-ruthenium ingathatha indawo yensimbi njenge-catalyst enokukhiqizwa kwamakhemikhali okuhle kodwa ngokuvamile ayisetshenziswa ngenxa yezindleko zayo zokubuyiselwa engxenyeni yokuxhumana.
* I-hydroquinone kanye nemikhiqizo yayo nayo ingalungiswa ngokuxutshwa kwama-phenols ahlukahlukene. Izibonelo zihlanganisa i-Elbs persulfate oxidation kanye ne-Dakin oxidation.
* I-Hydroquinone yatholakala okokuqala ngo-1820 ngamakhemikhali aseFrance uPelletier noCaventou ngokusebenzisa ukuhlunga okomile kwe-quinic acid.

## Ukusabela
Ukusabela kwamaqembu e-hydroquinone e-hydroidxyl kufana nokwezinye ama-phenols, njengoba kunesibindzi esiphansi. Isisekelo esiwumphumela esihlanganisiwe sibhekana ne-O-alkylation elula ukunikeza i-mono- ne-diethers. Ngokufanayo, i-hydroquinone ithinteka kakhulu ekushayweni kwendandatho yizinqubo ze-FriedelʹCrafts ezifana ne-alkylation. Le nqubo isetshenziswa endleleni ye-antioxidants ethandwayo njenge-2-tert-butyl-4-methoxyphenol (BHA). Udayi oyisibonakaliso we-quinizarin ukhiqizwa nge-diacylation ye-hydroquinone nge-phthalic anhydride.

### I-Redox
I-hydroquinone ihlangana ne-oxidation ngaphansi kwezimo ezincane ukuze inikeze i-benzoquinone. Le nqubo ingashintshwa. Ezinye izinhlobo ze-hydroquinone ezivela ngokwemvelo zibonisa lolu hlobo lokusabela, esinye isibonelo yi-coenzyme Q. Ezimbonini le nqubo isetshenziswa kokubili nge-hydrochinone uqobo kodwa kaningi ngezakhi zayo lapho i-OH eyodwa ithathelwe indawo yi-amine.

Lapho i-hydroquinone engenambala ne-benzoquinone, okuqinile okuphuzi okukhanyayo, kuhlanganiswa ngesilinganiso se-1:1, kwakheka i-dark-green crystalline charge-transfer complex (indawo yokuncibilikisa i-171 °C) ebizwa ngokuthi i-quinhydrone (C6H6O2·C6H4O2). Le nkimbinkimbi incibilika emanzini ashisayo, lapho ama-molecule amabili ehlukana khona ngenhlanganisela.

### Ukuvuselelwa
Ukusabela okubalulekile ukuguqulwa kwe-hydroquinone ibe yi-mono- ne-diamine derivatives. I-Methylaminophenol, esetshenziswa ekuthwebuleni izithombe, ikhiqizwa ngale ndlela:

: C6H4(OH)2 + \overset{methylamine}{CH3NH2} -> HOC6H4NHCH3 + H2O

Ama-diamines, awusizo embonini yenjoloba njenge-antiozone agents, akhiqizwa ngokufanayo nge-aniline:

: C6H4(OH)2  +  \overset{aniline}{2 C6H5NH2} ->  C6H4(N(H)C6H5)2  +  2 H2O

## Ukusetshenziswa
I-Hydroquinone inokusetshenziswa okuhlukahlukene okuhlobene ngokuyinhloko nokusebenza kwayo njengento yokunciphisa encibilikayo encibilekayo emanzini. Kuyingxenye eyinhloko kubathuthukisi abaningi bezithombe ezimnyama nezimhlophe zefilimu nephepha lapho, nge-metol eyingxube, inciphisa ama-halides esiliva abe yi-elemental silver.

Kuneminye imisebenzi ehlukahlukene ehlobene namandla ayo anciphisa. Njenge-inhibitor ye-polymerization, esebenzisa izakhiwo zayo ze-antioxidant, i-hydroquinone ivimbela i-polymerisation ye-acrylic acid, i-methyl methacrylate, i-cyanoacrylate, namanye ama-monomers athinteka kalula ku-radical-initiated polymerization. Ngokusebenza njenge-free radical scavenger, i-hydroquinone isebenza ukwelula isikhathi sokulondoloza inhlaka ezwela ukukhanya njenge-preceramic polymers.

I-Hydroquinone ingalahlekelwa yi-hydrogen cation kuwo womabili amaqembu e-hydroxyl ukuze yakhe i-diphenolate ion. Usawoti we-disodium diphenolate we-hydroquinone usetshenziswa njenge-comonomer unit eshintshanayo ekukhiqizeni i-polymer PEEK.

### Ukukhishwa kwesikhumba
I-Hydroquinone isetshenziswa njengendlela yokwenziwa kwesikhumba sibe mhlophe ukuze kuncishiswe umbala wesikhumba. Ayinawo amathuba afanayo okubangela i-dermatitis njenge-metol. Lesi yisithako esivela emithethweni yokwelapha kuphela kwamanye amazwe, kufaka phakathi amazwe angamalungu e-European Union ngaphansi kwe-Directives 76/768/EEC:1976.

Ngo-2006, i-United States Food and Drug Administration yahoxisa ukuvunyelwa kwayo kwangaphambili kwe-hydroquinone futhi yahlongoza ukuvinjelwa kwazo zonke izindlela zokulungiselela ezisemakethe. I-FDA yavimbela ngokusemthethweni i-hydroquinone ngo-2020 njengengxenye yenguquko enkulu yenqubo yokubuyekezwa kwemithi ngaphandle kwe-counter. I-FDA yathi i-hydroquinone ayikwazi ukukhipha njengento engase ibangele umdlavuza. Lesi siphetho safinyelelwa ngokusekelwe ezingeni lokumunca kubantu kanye nokwenzeka kwe-neoplasms emagundeni ocwaningweni oluningana lapho amagundane amadala atholakala khona enezinga eliphakeme lezimila, kufaka phakathi i-thyroid follicular cell hyperplasias, i-anisokaryosis (ukuguquguquka kobukhulu be-nucleus), i-mononuclear cell leukemia, i-hepatocellular adenomas kanye ne-renal tubule cell adenomas. Umkhankaso Wezimonyo Ezingaphephile nawo ugcizelele ukukhathazeka.

Ucwaningo oluningi luveze ukuthi i-hydroquinone, uma ithathwa ngomlomo, ingabangela i-exogenous ochronosis, isifo esiphazamisa lapho umbala oluhlaza okwesibhakabhaka-omnyama ufakwa esikhunjeni. Nokho, amalungiselelo esikhumba aqukethe isithako anikezwa endaweni. I-FDA yahlukanisa i-hydroquinone ngo-1982 njengomkhiqizo ophephile - ngokuvamile owaziwa njengophephile futhi osebenzayo (i-GRASE). Ngokubhekisela kwezinqumo ze-National Toxicology Program (i-NTP), ucwaningo olwengeziwe ngaphansi kwalo lwaphakanyiswa ukuze kutholakale ukuthi ngabe kunengozi kubantu ngokusetshenziswa kwe-hydroquinone. Ukuhlolwa kwe-NTP kwabonisa ubufakazi obuthile bemiphumela yesikhathi eside ye-carcinogenic ne-genotoxic

Ngenkathi i-hydroquinone isala inikezwa kabanzi ukwelashwa kwe-hyperpigmentation, imibuzo ephakamwe mayelana nesimo sayo sokuphepha ngama-ejensi alawulayo e-EU, eJapane, nase-USA ikhuthaza ukufunwa kwamanye ama-agent anokusebenza okufana. Amaningana anjalo asevele etholakala noma acwaningwe, kufaka phakathi i-azelaic acid, i-kojic acid, i'retinoids, i-cysteamine, i-topical steroids, i'glycolic acid, nezinye izinto. Enye yalezi, i-4-butylresorcinol, kuboniswe ukuthi isebenza kangcono ekwelapheni izifo zesikhumba ezihlobene ne-melanin ngamanani amakhulu, kanye nokuphephile ngokwanele ukuba itholakale phezu kwe-counter.

## Izenzakalo ezingokwemvelo
Ama-hydroquinones angenye ye-reactants emibili eyinhloko ezindlaleni zokuzivikela zamabhungane ama-bombardier, kanye ne-hydrogen peroxide (futhi mhlawumbe nezinye izakhi, kuye ngezinhlobo), eziqoqa emthonjeni. I-tank ivula nge-valve elawulwa imisipha iye egunjini lokusabela elinezindonga eziwugqinsi. Leli gumbi ligcwele amangqamuzana akhipha ama-catalases nama-peroxidases. Lapho okuqukethwe kuleli thange kuphoqelelwa ukuba kungene egunjini lokuhlangana, ama-catalases nama-peroxidases ngokushesha abulala i-hydrogen peroxide futhi akhuthaze i-oxidation yama-hydroquinones abe ama-p-quinones. Lezi zinguquko zikhipha umoya-mpilo okhululekile futhi zikhiqize ukushisa okwanele ukuletha ingxube endaweni yokubila. Bese ihwamuka cishe ingxenye yesihlanu yayo, ikhiqize ukufafaza okushisayo esiswini sebhungane.

I-Hydroquinone kucatshangwa ukuthi iyisihlungu esinamandla kumakhowe e-Agaricus hondensis.

I-Hydroquinone iboniswe ukuthi ingenye yezakhi zamakhemikhali zomkhiqizo wemvelo we-propolis.

Futhi ingenye yezakhi zamakhemikhali ezitholakala ku-castoreum. Lesi sakhiwo siqoqwa ezikhwameni ze-beaver.

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