Thermal, photochemical, and photonucleated thermal dehydration of p-hydroxytriarylmethanols in solids. (3,5-Dimethyl-4-hydroxyphenyl)diphenylmethanol and (3,5-dibromo-4-hydroxyphenyl)diphenylmethanol. X-ray crystal structures of (4-hydroxyphenyl)diphenylmethanol and its 3,5-dimethyl derivative

Lewis, Terry W.; Curtin, David Y.; Paul, Iain C.

doi:10.1021/ja00513a043

Cited by 25 publications

(13 citation statements)

References 7 publications

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“…These characteristics, which were observed for several different samples, are suggestive of a phase transition of form (1¢~) converting to (1/3) at a temperature less than 383 K. It appears that grinding of crystals of (1~0 prior to heating was necessary to effect the transformation. It should be noted that the product of the solid-state dehydration of (2) is microcrystalline and gives a powder pattern corresponding to that of form (lfl) (Lewis, Curtin & Paul, 1979). No evidence was found for the intermediacy of (l a) in this dehydration.…”

Section: Evidence For a Possible Phase Transitionmentioning

confidence: 92%

“…The synthesis and characterization of 2,6-dimethyl-4-(a,a-diphenylmethylene)-1,4-benzoquinone (1) was described previously (Lewis, Curtin & Paul, 1979).…”

Section: Methodsmentioning

confidence: 99%

“…Experiments were conducted with the hope of finding some evidence for the intermediacy of (1 st) in the solidstate thermal dehydration of (2) to (1) [the form obtained is (lfl)] (Lewis, Curtin & Paul, 1979). Both single crystals of (2) and microcrystalline samples of (2) were heated at 383 K for lengths of time less than those necessary for the complete dehydration of (2) to occur.…”

Section: X-ray Powder Photographsmentioning

confidence: 99%

“…An interesting example showing many of the above phenomena is the case of binaphthyi Pincock, Perkins, Ma & Wilson, 1971). We became interested in the crystal structure of (1) as it is the product of a solid-state dehydration of (4-hydroxy-2,5-dimethylphenyl)diphenylmethanol (2) (Lewis, Curtin & Paul, 1979). In the course of these investigations we discovered that at least three singlecrystal forms of (1) could be obtained.…”

Section: Introductionmentioning

confidence: 99%

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Molecular and crystal structures of the α and β forms of 2,6-dimethyl-4-(α,α-diphenylmethylene)-1,4-benzoquinone (2,6-dimethylfuchsone): evidence for the thermal conversion of the racemic crystals (1α) to the chiral crystals (1β)

Lewis¹,

Paul²,

Curtin³

1980

Acta Crystallogr Sect B

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The crystal structures of two modifications of 2,6-dimethyl-4-(a,a-diphenylmethylene)-1,4-benzoquinone (2,6-dimethylfuchsone) (1) have been determined. One of the forms, (I a), belongs to the space group P2 t/c with a = 8.531 (2), b = 18.677 (5), c = 10.021 (1) A, fl = 90.87 (2) °, Z = 4, and has been refined to an R factor of 0.053 on 1992 non-zero reflections. The other form, (lfl), belongs to the space group P2~2t2 t with a = 8.156 (2), b = 17.761 (4), c = 10.959 (1) A, Z = 4 and has been refined to an R factor of 0.045 on 1452 nonzero reflections. The molecular structures of (1) in the forms (la) and (lfl) are almost identical, and, in the conformation found in the crystal, the molecules exhibit chirality. In both crystals, molecules of the same chirality pack in layers that are almost identical. However, the relationship between adjacent layers is different in the two forms, involving only congruent operations in the (lfl) form, while enantiomorphic operations are involved in the (la) form. Some evidence for a phase transition from the racemic (l a) to the chiral (lfl) is presented. Changes are observed on powder pictures when a ground sample thought to contain (la) and (lfl) is heated to 383 K. These changes can be explained by conversion of (la) to (lfl).

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Section: Evidence For a Possible Phase Transitionmentioning

confidence: 92%

“…The synthesis and characterization of 2,6-dimethyl-4-(a,a-diphenylmethylene)-1,4-benzoquinone (1) was described previously (Lewis, Curtin & Paul, 1979).…”

Section: Methodsmentioning

confidence: 99%

Section: X-ray Powder Photographsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Molecular and crystal structures of the α and β forms of 2,6-dimethyl-4-(α,α-diphenylmethylene)-1,4-benzoquinone (2,6-dimethylfuchsone): evidence for the thermal conversion of the racemic crystals (1α) to the chiral crystals (1β)

Lewis¹,

Paul²,

Curtin³

1980

Acta Crystallogr Sect B

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“…26 Lewis sa svojim suradnicima ponovno je studirao tu reakciju 1970-ih godina. 27 Iz kristalne strukture spoja 21 (slika 3) otkriveno je zašto je fotodehidratacija u čvrstom stanju moguća: fenolna i benzilna OH-skupina su u vodikovoj vezi unutar kristala, te u pobuđenom stanju dolazi do prijenosa protona s fenolne na benzilnu OH-skupinu, što je praćeno dehidratacijom. Sličnu reakciju dehidratacije 1970-ih godina studirao je Hamai (shema 7).…”

Section: Fotodehalogenacija Derivata Fenolaunclassified

Kinon-metidi (II. dio): Fotokemijsko generiranje i razvoj primjene u fotokemoterapiji

2017

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često prisutni u kemiji i fotokemiji fenola i njima srodnih spojeva.1 Osim vrlo široke primjene u organskoj sintezi, 2,3važna mogućnost primjene je i u biološkim sustavima, ponajprije kao antitumorskih agensa. 4 Potrebu za prouča-vanjem i razumijevanjem kemije QM-a, kao i studiranje njihove potencijalne primjenjivosti u biološkim sustavima pokazuju rezultati do kojih se do sada došlo na Institutu Ruđer Bošković 5,6,7,8,9,10 i u grupi M. Freccera. 6a,11 Kako su QM reaktivni međuprodukti kratkog vremena života, uobičajeno je da se generiraju 3 iz nekog pogodnog prekursora. To se može postići upotrebom odgovarajućih reagensa ili grijanjem (sintetske ili termičke metode).3 Kako u biološ-kim sustavima najčešće nije baš pogodno upotrebljavati takve reagense, fotokemijske metode generiranja QM-a tu postižu veliku prednost. Iz pogodnog prekursora može se nakon pobude svjetlom određene valne duljine generirati QM. Prednost toga je da se QM generira samo tada kad se to želi i samo na mjestu gdje je osvjetljeno. Međutim, kako bi QM mogli imati praktičnu primjenu u medicini, potrebno je pronaći sustave koji bi mogli dati QM nakon pobuđivanja svjetlom u vidljivom području, idealno iznad 500 nm, ili barem svjetlom > 350 nm, koje ne apsorbiraju uobičajene unutarstanične molekule. Primjeri prekursora QM-a koje bi se moglo pobuditi vidljivim dijelom spektra nisu do sada opisani u literaturi. Fotokemijske metode generiranja QM-aU fotokemijskim reakcijama sudjeluju vrste koje su elektronski pobuđene, zbog čega imaju znatno različitu raspodjelu elektrona u molekuli nego što je to slučaj u osnovnom stanju te je i reaktivnost u pobuđenom stanju drugačija nego u osnovnom stanju. Derivati fenola i fenilnih etera ili laktona koji podliježu ß-cijepanju najčešće se upotrebljavaju za generiranje QM-a u fotokemijskim reakcijama.Takav tip reakcija poznat je još iz pionirskog rada Zimmermana, koji je studirao reakcije solvolize s nukleofilnim otapalom, tj. nukleofilne supstitucije skupine vezane u ß-položaju u odnosu na kromofor.12 Mehanizam reakcije kod aromatskih spojeva, prema poznatim literaturnim podacima, može uključivati nastanak arilnih karbokationa, 13 karbena 14 ili homolitičko cijepanje veze praćeno prijenosom elektrona.15 Iako se odvijaju različitim mehanizmom od reakcija u aromatskim spojevima, 12 takve reakcije uobičajene su i u fotokemiji mnogih karbonilnih spojeva.16 U nastavku će biti naveden pregled reakcija fotokemijskog generiranja QM-a. Fotofragmentacija oksaheterocikalaJedna od prvih opisanih metoda fotokemijskog generiranja QM-a bila je fotofragmentacija oksaheterocikala. Chapman i sur. studirali su generiranje QM-a iz benzolaktona 1, i sulfona 4. Nakon fotopobude i eliminacije male molekule (CO ili SO 2 ) nastaje QM, koji odmah reagira s prisutnim nukleofilnim otapalom -metanolom, dajući o-hidroksibenzil-metil-eter (3) kao produkt reakcije fotosolvolize (shema 1). U Diels-Alderovoj reakciji [4+2] cikloadicije QM-a 2 i 1,1-dimetoksieten (5) daju kroman 6, čijom izolacijom je na neizravan način dokazano postojanje QM-a...

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Interrelationships between phase transformations and organic chemical reactivity in the solid state

Shalaev¹,

Zografi²

1996

J. Phys. Org. Chem.

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A qualitative analysis is presented of the interrelationships between phase transformations and organic chemical reactivity in the solid state, taking into consideration general thermochemical relationships and the thermodynamics of heterophase equilibrium. Two cases, where isomerization reactions depend on the solid-state solubility of the reactant and product, are considered and show that the formation of a new phase can influence both the reaction yield and rate. For example, it is shown that crystallization of a new phase from a crystalline or amorphous solid solution can supply the thermodynamic driving force for chemical transformation. Formation of a new phase may influence solid-state kinetics depending on the solubility of a reactant in the new phase and the relative rates of chemical transformation and formation of the new phase. It is further shown that even for simple monomolecular reactions, kinetic curves for the overall process can consist of up to five parts, depending on the type of phase diagram involved. These principles have been applied to some examples of solid-state isomerization in a way that allows the choice of a proper kinetic scheme and an explanation of the direction and maximum yield observed for a particular reaction.

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Thermal, photochemical, and photonucleated thermal dehydration of p-hydroxytriarylmethanols in solids. (3,5-Dimethyl-4-hydroxyphenyl)diphenylmethanol and (3,5-dibromo-4-hydroxyphenyl)diphenylmethanol. X-ray crystal structures of (4-hydroxyphenyl)diphenylmethanol and its 3,5-dimethyl derivative

Cited by 25 publications

References 7 publications

Molecular and crystal structures of the α and β forms of 2,6-dimethyl-4-(α,α-diphenylmethylene)-1,4-benzoquinone (2,6-dimethylfuchsone): evidence for the thermal conversion of the racemic crystals (1α) to the chiral crystals (1β)

Molecular and crystal structures of the α and β forms of 2,6-dimethyl-4-(α,α-diphenylmethylene)-1,4-benzoquinone (2,6-dimethylfuchsone): evidence for the thermal conversion of the racemic crystals (1α) to the chiral crystals (1β)

Kinon-metidi (II. dio): Fotokemijsko generiranje i razvoj primjene u fotokemoterapiji

Interrelationships between phase transformations and organic chemical reactivity in the solid state

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