氦合氢离子

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氦合氢离子
系统名
Hydridohelium(1+)[1]
识别
ChemSpider 21106447
SMILES
Gmelin 2
ChEBI 33688
性质
化学式 HeH+
摩尔质量 5.01054 g mol-1 g·mol⁻¹
精确质量 5.010428282 g mol-1
若非注明,所有数据均出自一般条件(25 ℃,100 kPa)下。

氦合氢离子,化学式为HeH+,是一个带正电的离子。它首次发现于1925年,通过质子(或氢离子)和原子在气相中反应制得。[2]它是已知最强的布朗斯特质子酸质子亲和能为177.8 kJ/mol。[3]这种离子也被称为氦氢分子离子。有人认为,这种物质可以存在于自然星际物质中。[4]这是最简单的异核离子,可以与同核的氢分子离子H2+相比较。与H2+不同的是,它有一个永久的键偶极矩,使它更容易表现出光谱特征。[5]

性质[编辑]

HHe+不能在凝聚相中制备,因为这会使它与任何阴离子、分子、原子发生作用。但是,可以用盖斯定律预测它在水溶液中的酸性:

HHe+(g) H+(g) + He(g) +178 kJ/mol [3]
HHe+(aq) HHe+(g)   +973 kJ/mol [6]
H+(g) H+(aq)   – 1530 kJ/mol  
He(g) He(aq)   +19 kJ/mol [7]
HHe+(aq) H+(aq) + He(aq) – 360 kJ/mol  

电离过程–360 kJ/mol的自由能变化相当于pKa为-63。

HeH+共价键的长度是0.772Å[8]

其他氦氢离子已经知道或者在理论上研究。HeH2+,已经被微波光谱观测到,[9]科学家计算出它的亲和能为6 kcal/mol,而HeH3+为0.1 kcal/mol。[10]

中性分子[编辑]

不同于氦合氢离子,氢和氦构成的中性分子在一般情况下是很不稳定的。但是,它作为一个准分子在激发态是稳定的,于20世纪80年代中期首次在光谱中观测到。[11][12][13]

参考资料[编辑]

除非另外提及,数据取自Weast, R. C. (Ed.) (1981). CRC Handbook of Chemistry and Physics (62nd Edn.). Boca Raton, FL: CRC Press. ISBN 0-8493-0462-8.

  1. ^ hydridohelium(1+) (CHEBI:33688). Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute. 
  2. ^ T. R. Hogness and E. G. Lunn. The Ionization of Hydrogen by Electron Impact as Interpreted by Positive Ray Analysis. Physical Review. 1925, 26: 44–55. doi:10.1103/PhysRev.26.44. 
  3. ^ 3.0 3.1 Lias, S. G.; Liebman, J. F.; Levin, R. D. Evaluated Gas Phase Basicities and Proton Affinities of Molecules; Heats of Formation of Protonated Molecules. Journal of Physical and Chemical Reference Data. 1984, 13: 695. doi:10.1063/1.555719. 
  4. ^ J. Fernandez; F. Martin. Photoionization of the HeH+ molecular ion. J. Phys. B: At. Mol. Opt. Phys. 2007, 40: 2471–2480. doi:10.1088/0953-4075/40/12/020. 
  5. ^ Coxon, J; Hajigeorgiou, PG. Experimental Born–Oppenheimer Potential for theX1Σ+Ground State of HeH+: Comparison with theAb InitioPotential. Journal of Molecular Spectroscopy. 1999, 193 (2): 306. doi:10.1006/jmsp.1998.7740. PMID 9920707. 
  6. ^ Estimated to be the same as for Li+(aq) → Li+(g).
  7. ^ Estimated from solubility data.
  8. ^ Coyne, John P.; Ball, David W. Alpha particle chemistry. On the formation of stable complexes between He2+ and other simple species: implications for atmospheric and interstellar chemistry. Journal of Molecular Modeling. 2009, 15 (1): 37. doi:10.1007/s00894-008-0371-3. PMID 18936986. 
  9. ^ Alan Carrington, David I. Gammie, Andrew M. Shaw, Susie M. Taylor and Jeremy M. Hutson. Observation of a microwave spectrum of the long-range He···H2+ complex. Chemical Physics Letters. 1996, 260: 395–405. doi:10.1016/0009-2614(96)00860-3. 
  10. ^ F.Pauzat and Y. Ellinger Where do noble gases hide in space?, Astrochemistry: Recent Successes and Current Challenges, Poster Book IAU Symposium No. 231, 2005 A. J. Markwick-Kemper (ed.)
  11. ^ Thomas Möller, Michael Beland, and Georg Zimmerer. Observation of Fluorescence of the HeH Molecule. Phys. Rev. Lett. 1985, 55 (20): 2145–2148. doi:10.1103/PhysRevLett.55.2145. PMID 10032060. 
  12. ^ Wolfgang Ketterle, The Nobel Prize in Physics 2001
  13. ^ W. Ketterle, H. Figger, and H. Walther. Emission spectra of bound helium hydride. Phys. Rev. Lett. 1985, 55 (27): 2941–2944. doi:10.1103/PhysRevLett.55.2941. PMID 10032281.