it is reported that converted to acid through KMNO4 and 50% pyidine at room temp but m.p was not clear in the paper while trying the other method KMNO4 excess and heating at 80 , different spotting why any other susceptible gp for oxidation , please help
it is reported that converted to acid through KMNO4 and 50% pyidine at room temp but m.p was not clear in the paper while trying the other method KMNO4 excess and heating at 80 , different spotting why any other susceptible gp for oxidation , please help
1a). Under acidic aqueous conditions: KMnO4 → MnO2 → Mn2+ 1b). Under basic aqueous conditions: KMnO4 → MnO2 → Mn(OH)2 → Mn Please, take a look to the above half equations and the corresponding voltages, from tables of various sources and then, you will clearly understand the role of pyridine. 2). During oxidation reaction, the oxidant is added in accordance of the oxidation number equilibrium and not at a molar ratio. 3). Thiophene oxidation steps: Thiophene S-oxide→Thiophene S,S-dioxide→Semisuccinic-suflonic acid (HO3SCH2CH2CO2H) 4). During oxidation reaction, nitrogen containing moieties might be oxidized to the corresponding N-oxides by the excess of the oxidizing agent. However, low amounts of N-oxides side products, can be reduced by shaking with fresh iron powder or fresh zinc powder (Attention: this might be dangerous with flammable solvents (low flash point) and in absence of water}. 5). According the “good laboratory practice” and in a multi-step synthesis, a compound must be highly purified before being introduced in the next step (that makes life, easy). Especially in cases of biological and pharmaceutical interest, where the purity of the product is more important than the yield.
1a). Under acidic aqueous conditions: KMnO4 → MnO2 → Mn2+ 1b). Under basic aqueous conditions: KMnO4 → MnO2 → Mn(OH)2 → Mn Please, take a look to the above half equations and the corresponding voltages, from tables of various sources and then, you will clearly understand the role of pyridine. 2). During oxidation reaction, the oxidant is added in accordance of the oxidation number equilibrium and not at a molar ratio. 3). Thiophene oxidation steps: Thiophene S-oxide→Thiophene S,S-dioxide→Semisuccinic-suflonic acid (HO3SCH2CH2CO2H) 4). During oxidation reaction, nitrogen containing moieties might be oxidized to the corresponding N-oxides by the excess of the oxidizing agent. However, low amounts of N-oxides side products, can be reduced by shaking with fresh iron powder or fresh zinc powder (Attention: this might be dangerous with flammable solvents (low flash point) and in absence of water}. 5). According the “good laboratory practice” and in a multi-step synthesis, a compound must be highly purified before being introduced in the next step (that makes life, easy). Especially in cases of biological and pharmaceutical interest, where the purity of the product is more important than the yield.
Excess of KMnO4 in acid may further oxidize thiophene to S,S-dioxide and even pyrazole to N–oxides. Pyridine is a base that stops KMnO4 reduction to MnO2 instead of Mn2+ and thus, KMNO4 in aqueous pyridine is a milder oxidizing agent. Nitrogen containing polar molecules often form waxy solids, when dissolved in n-hexane. Try another recrystallization solvent system.
Excess of KMnO4 in acid may further oxidize thiophene to S,S-dioxide and even pyrazole to N–oxides. Pyridine is a base that stops KMnO4 reduction to MnO2 instead of Mn2+ and thus, KMNO4 in aqueous pyridine is a milder oxidizing agent. Nitrogen containing polar molecules often form waxy solids, when dissolved in n-hexane. Try another recrystallization solvent system.
thank u Sir , i get it know but l had a further question did the N give oxide even it has complete valency and did SO2 of the thienyl ring stable for futher estrification and acid hydrazide formation also the ester was pure so enters into rection directly with no crystallization but its problem is when acid and alchol and SOCL2 added is turns greeny waxy during reflux and after sepration did u think is it the effect of residual pyridine from the step b4 but SOCl2 is acidic and neutralize any xss pyridine also ester m.p= 80 or less and another question in all cases KMNO4 converted to Mno2 upon any reaction in presence or absence of pyridine specially i tried this method xss and heating in another derivative (CH3 instead of theinyl ring )it was reported and works?
thank u Sir , i get it know but l had a further question did the N give oxide even it has complete valency and did SO2 of the thienyl ring stable for futher estrification and acid hydrazide formation also the ester was pure so enters into rection directly with no crystallization but its problem is when acid and alchol and SOCL2 added is turns greeny waxy during reflux and after sepration did u think is it the effect of residual pyridine from the step b4 but SOCl2 is acidic and neutralize any xss pyridine also ester m.p= 80 or less and another question in all cases KMNO4 converted to Mno2 upon any reaction in presence or absence of pyridine specially i tried this method xss and heating in another derivative (CH3 instead of theinyl ring )it was reported and works?
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KMnO4 → MnO2 → Mn2+
1b). Under basic aqueous conditions:
KMnO4 → MnO2 → Mn(OH)2 → Mn
Please, take a look to the above half equations and the corresponding voltages, from tables of various sources and then, you will clearly understand the role of pyridine.
2). During oxidation reaction, the oxidant is added in accordance of the oxidation number equilibrium and not at a molar ratio.
3). Thiophene oxidation steps:
Thiophene S-oxide→Thiophene S,S-dioxide→Semisuccinic-suflonic acid (HO3SCH2CH2CO2H)
4). During oxidation reaction, nitrogen containing moieties might be oxidized to the corresponding N-oxides by the excess of the oxidizing agent. However, low amounts of N-oxides side products, can be reduced by shaking with fresh iron powder or fresh zinc powder (Attention: this might be dangerous with flammable solvents (low flash point) and in absence of water}.
5). According the “good laboratory practice” and in a multi-step synthesis, a compound must be highly purified before being introduced in the next step (that makes life, easy). Especially in cases of biological and pharmaceutical interest, where the purity of the product is more important than the yield.
KMnO4 → MnO2 → Mn2+
1b). Under basic aqueous conditions:
KMnO4 → MnO2 → Mn(OH)2 → Mn
Please, take a look to the above half equations and the corresponding voltages, from tables of various sources and then, you will clearly understand the role of pyridine.
2). During oxidation reaction, the oxidant is added in accordance of the oxidation number equilibrium and not at a molar ratio.
3). Thiophene oxidation steps:
Thiophene S-oxide→Thiophene S,S-dioxide→Semisuccinic-suflonic acid (HO3SCH2CH2CO2H)
4). During oxidation reaction, nitrogen containing moieties might be oxidized to the corresponding N-oxides by the excess of the oxidizing agent. However, low amounts of N-oxides side products, can be reduced by shaking with fresh iron powder or fresh zinc powder (Attention: this might be dangerous with flammable solvents (low flash point) and in absence of water}.
5). According the “good laboratory practice” and in a multi-step synthesis, a compound must be highly purified before being introduced in the next step (that makes life, easy). Especially in cases of biological and pharmaceutical interest, where the purity of the product is more important than the yield.
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Nitrogen containing polar molecules often form waxy solids, when dissolved in n-hexane. Try another recrystallization solvent system.
Nitrogen containing polar molecules often form waxy solids, when dissolved in n-hexane. Try another recrystallization solvent system.
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also the ester was pure so enters into rection directly with no crystallization but its problem is when acid and alchol and SOCL2 added is turns greeny waxy during reflux and after sepration did u think is it the effect of residual pyridine from the step b4 but SOCl2 is acidic and neutralize any xss pyridine also ester m.p= 80 or less
and another question in all cases KMNO4 converted to Mno2 upon any reaction in presence or absence of pyridine specially i tried this method xss and heating in another derivative (CH3 instead of theinyl ring )it was reported and works?
also the ester was pure so enters into rection directly with no crystallization but its problem is when acid and alchol and SOCL2 added is turns greeny waxy during reflux and after sepration did u think is it the effect of residual pyridine from the step b4 but SOCl2 is acidic and neutralize any xss pyridine also ester m.p= 80 or less
and another question in all cases KMNO4 converted to Mno2 upon any reaction in presence or absence of pyridine specially i tried this method xss and heating in another derivative (CH3 instead of theinyl ring )it was reported and works?
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