Radical cations in the OH-radical-induced oxidation of thiourea acid tetramethylthiourea in aqueous solution

CORC > 上海应用物理研究所 > 中国科学院上海应用物理研究所 > 中科院上海原子核所2003年前

	Radical cations in the OH-radical-induced oxidation of thiourea acid tetramethylthiourea in aqueous solution
	Wang, WF（王文峰） ; Schuchmann, MN ; Schuchmann, HP ; Knolle, W ; von Sonntag, J ; von Sonntag, C
刊名	JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
	1999
卷号	121 期号:1 页码:238
ISSN号	0002-7863
英文摘要	Hydroxyl radicals were generated radiolytically in N(2)O-saturated aqueous solutions of thiourea and tetramethylthiourea. The rate constant of the reaction of OH radicals with thiourea (tetramethylthiourea) has been determined using 2-propanol as well as NaN(3) as competitors to be 1.2 x 10(10) dm(3) mol(-1) s(-1) (8.0 x 10(9) dm(3) mol(-1) s(-1)). A transient appears after a short induction period and shows a well-defined absorption spectrum with lambda(max) = 400 nm (epsilon = 7400 dm(3) mol(-1) cm(-1)); that of tetramethylthiourea has lambda(max) = 450 nm (epsilon = 6560 dm(3) mol(-1) cm(-1)). Using conductometric detection, it has been shown that, in both cases, OH(-) and a positively charged species are produced. These results indicate that a radical cation is formed. These intermediates with lambda(max) = 400 nm (450 nm) are not the primary radical cations, since the intensity of the absorbance depends on the substrate concentration. The absorbance build-up follows a complex kinetics best described by the reversible formation of a dimeric radical cation by addition of a primary radical cation to a molecule of thiourea. The equilibrium constant for this addition has been determined by competition kinetics to be 5.5 x 10(5) dm(3) mol(-1) for thiourea (7.6 x 10(4) dm(3) mol(-1) for tetramethylthiourea). In the bimolecular decay of the dimeric radical cation (thiourea, 2k = 9.0 x 10(8) dm(3) mol(-1) s(-1); tetramethylthiourea, 1.3 x 10(9) dm(3) mol(-1) s(-1)), formamidine (tetramethylformamidine) disulfide is formed. In basic solutions of thiourea, the absorbance at 400 nm of the dimeric radical cation decays rapidly, giving rise (5.9 x 10(7) dm(3) mol(-1) s(-1)) to a new intermediate with a broad maximum at 510 nm (epsilon = 750 dm(3) mol(-1) cm(-1)). This reaction is not observed in tetramethylthiourea. The absorption at 510 nm is attributed to the formation of a dimeric radical anion, via neutralization of the dimeric radical cation and subsequent deprotonation of the neutral dimeric radical. The primary radical cation of thiourea is deprotonated by OH- (2.8 x 10(9) dm(3) mol(-1) s(-1)) to give a neutral thiyl radical. The latter reacts rapidly with thiourea, yielding a dimeric radical, which is identical to the species from the reaction of OH(-) with the dimeric radical cation. The dimeric radical cations of thiourea and tetramethylthiourea are strong oxidants and readily oxidize the superoxide radical (4.5 x 10(9) dm(3) mol(-1) s(-1) for thiourea and 3.8 x 10(9) dm(3) mol(-1) s(-1) for tetramethylthiourea), phenolate ion (3 x 10(8) dm(3) mol(-1) s(-1) for tetramethylthiourea), and even azide ion (4 x 10(6) dm(3) mol(-1) s(-1) for thiourea and similar to 10(6) dm(3) mol(-1) s(-1) for tetramethylthiourea). With Oar the dimeric radical cation of thiourea reacts relatively slowly (1.2 x 107 dm(3) mol(-1) s(-1)) and reversibly (2 x 10(3) s(-1)).
收录类别	SCI
语种	英语
WOS记录号	WOS:000078079200028
公开日期	2012-09-25
内容类型	期刊论文
源URL	[http://ir.sinap.ac.cn/handle/331007/10137]
专题	上海应用物理研究所_中科院上海原子核所2003年前
推荐引用方式 GB/T 7714	Wang, WF,Schuchmann, MN,Schuchmann, HP,et al. Radical cations in the OH-radical-induced oxidation of thiourea acid tetramethylthiourea in aqueous solution[J]. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY,1999,121(1):238.
APA	Wang, WF,Schuchmann, MN,Schuchmann, HP,Knolle, W,von Sonntag, J,&von Sonntag, C.(1999).Radical cations in the OH-radical-induced oxidation of thiourea acid tetramethylthiourea in aqueous solution.JOURNAL OF THE AMERICAN CHEMICAL SOCIETY,121(1),238.
MLA	Wang, WF,et al."Radical cations in the OH-radical-induced oxidation of thiourea acid tetramethylthiourea in aqueous solution".JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 121.1(1999):238.