Arsole: Difference between revisions

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{{Short description|Chemical compound}}

[[Image:Arsole.png|thumb|80px|right|Chemical structure of Arsole]]

{{Chembox

:''This article refers to the chemical compound. For the phrase referring to the anus or a contemptible person, see [[asshole]]''

| Watchedfields = changed

----

| verifiedrevid = 443401483

'''Arsole''' is a [[chemical compound]] of the [[chemical formula|formula]] C₄H₅As. The structure is like [[pyrrole]] except that an [[arsenic]] atom is substituted for the [[nitrogen]] atom and that arsole is not [[aromatic]]. Arsole itself has not yet been [[Chemical synthesis|synthesized]], but several [[substitution (chemistry)|substituted]] analogs called '''arsoles''' do exist.

| ImageFileL1 = Arsole.png

| ImageClassL1 = skin-invert-image

| ImageSizeL1 = 121

| ImageNameL1 = Structural formula of arsole with an implicit hydrogen

| ImageFileR1 = Arsole-Spartan-MP2-3D-balls-B.png

| ImageClassR1 = bg-transparent

| ImageSizeR1 = 121

| ImageNameR1 = Ball-and-stick model of the arsole molecule

| PIN = 1''H''-Arsole

| OtherNames = Arsenole<br />

Arsacyclopentadiene

| Section1 = {{Chembox Identifiers

| CASNo = 287-77-4

| CASNo_Ref = {{cascite|correct|??}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = AH6RG8546R

| ChemSpiderID = 16787685

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChEBI_Ref = {{ebicite|correct|EBI}}

| ChEBI = 33131

| PubChem = 6398625

| SMILES = [AsH]1C=CC=C1

| StdInChI = 1S/C4H5As/c1-2-4-5-3-1/h1-5H

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

| InChI = 1/C4H5As/c1-2-4-5-3-1/h1-5H

| StdInChIKey = NXHAKHHKDBVHPV-UHFFFAOYSA-N

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| InChIKey = NXHAKHHKDBVHPV-UHFFFAOYAK}}

| Section2 = {{Chembox Properties

| Formula = C₄H₅As

| MolarMass = 128.00 g mol⁻¹}}

| Section8 = {{Chembox Related

| OtherCompounds = [[Pyrrole]], [[phosphole]], [[bismole]], [[stibole]]}}

}}

'''Arsole''', also called '''arsenole'''<ref>{{harvnb|Mann|1970}}: "In English this ring system has frequently named arsenole 'for euphony'."</ref> or '''arsacyclopentadiene''', is an [[organoarsenic compound]] with the [[chemical formula|formula]] C₄H₅As. It is classified as a [[metallole]] and is isoelectronic to and related to [[pyrrole]] except that an [[arsenic]] atom is substituted for the [[nitrogen]] atom. Whereas the pyrrole molecule is planar, the arsole molecule is not, and the hydrogen atom bonded to arsenic extends out of the molecular plane. Arsole is only moderately [[aromatic]], with about 40% the aromaticity of pyrrole.<ref name=rev/> Arsole itself has not been reported in pure form, but several [[substitution (chemistry)|substituted]] analogs called '''arsoles''' exist. Arsoles and more complex arsole derivatives have similar structure and chemical properties to those of [[phosphole]] derivatives. When arsole is fused to a [[benzene]] ring, this molecule is called '''arsindole''', or benzarsole.<ref>{{cite journal|journal = [[J. Phys. Chem. A]]|year = 2009|volume = 113|issue = 2|pages = 464–473|title = Effect of Periodic Replacement of the Heteroatom on the Spectroscopic Properties of Indole and Benzofuran Derivatives|author1=A. Muranaka |author2=S. Yasuike |author3=C.-Y. Liu |author4=J. Kurita |author5=N. Kakusawa |author6=T. Tsuchiya |author7=M. Okuda |author8=N. Kobayashi |author9=Y. Matsumoto |author10=K. Yoshida |author11=D. Hashizume |author12=M. Uchiyama |doi = 10.1021/jp8079843|pmid = 19099440| bibcode=2009JPCA..113..464M }}</ref>

== See also Nomenclature==

Arsole belongs to the series of heterocyclic [[pnictogen]] compounds.

The naming of cyclic [[Organoarsenic chemistry|organoarsenic compounds]] such as arsole is based on an extension of the [[Hantzsch–Widman nomenclature]] system<ref>"[http://www.chem.qmul.ac.uk/iupac/hetero/HW.html Revision of the Extended Hantzsch-Widman System of Nomenclature for Heteromonocycles] {{Webarchive|url=https://web.archive.org/web/20170908125656/http://www.chem.qmul.ac.uk/iupac/hetero/HW.html |date=2017-09-08 }}" at IUPAC, retrieved 29 Sept 2008</ref> approved by [[IUPAC]], as summarized below:<ref>{{cite book|author=Nicholas C. Norman|title=Chemistry of arsenic, antimony, and bismuth|url=https://books.google.com/books?id=vVhpurkfeN4C&pg=PA235|accessdate=15 March 2011|year=1998|publisher=Springer|isbn=978-0-7514-0389-3|page=235}}</ref>

{| class="wikitable" style="text-align:center"

!Ring size!![[Unsaturated hydrocarbon|Unsaturated ring]]!![[Saturated and unsaturated compounds|Saturated ring]]

|-

| 3||Arsirene||Arsirane

|-

| 4||Arsete||Arsetane

|-

| 5||'''Arsole'''||Arsolane

|-

| 6||[[Arsinine]]||Arsinane

|-

| 7||Arsepine||Arsepane

|-

| 8||Arsocine||Arsocane

|-

| 9||Arsonine||Arsonane

|-

| 10||Arsecine||Arsecane

|}

Because of its similarity to the English slang word "[[arsehole]]" (in common use outside North America), the name "arsole" has been considered a target of fun, a "silly name",<ref>{{cite book|author=Richard Watson Todd|title=Much ado about English: up and down the bizarre byways of a fascinating language|url=https://books.google.com/books?id=zb-ISQHfz70C&pg=PA138|accessdate=15 March 2011|date=25 May 2007|publisher=Nicholas Brealey Publishing|isbn=978-1-85788-372-5|page=138}}</ref><ref>Paul W May, ''Molecules with Silly or Unusual Names'', publ. 2008 Imperial College Press, {{ISBN|978-1-84816-207-5}}(pbk). See also the Web page "[http://www.chm.bris.ac.uk/sillymolecules/sillymols.htm Molecules with Silly or Unusual Names] {{Webarchive|url=https://web.archive.org/web/20090907132040/http://www.chm.bris.ac.uk/sillymolecules/sillymols.htm |date=2009-09-07 }}" at the School of Chemistry, University of Bristol, (retrieved 29 Sept 2008)</ref> and one of several [[List of chemical compounds with unusual names|chemical compounds with an unusual name]]. However, this "silly name" coincidence has also stimulated detailed scientific studies.<ref name=rev>{{cite journal|journal = Lett. Org. Chem.|volume = 2|year = 2005|pages = 469–474|author1=M. P. Johansson |author2=J. Juselius |title = Arsole Aromaticity Revisited|issue = 5|doi = 10.2174/1570178054405968|quote=Using quantum chemical methodology, we reinvestigate the aromaticity of the much debated arsole, using the newly developed gauge-including magnetically induced currents (GIMIC) method. GIMIC provides a quantitative measure of the induced ring current strength, showing arsole to be moderately aromatic.}}</ref>{{failed verification|date=September 2020}}{{dubious|date=September 2020}}

* [[Pyrrole]], a [[nitrogen]] analog.

* [[Furan]], an [[oxygen]] analog.

* [[Thiophene]], a [[sulfur]] analog.

* [[Simple aromatic rings]]

* Varsole, a [[petroleum]] [[Distillation|distillate]] with a [[boiling point|boiling range]] of 150 - 200 °C.

==Properties==

== External references ==

{|class="wikitable" style="text-align:center; float:right;margin-left:0.5em"

|+Calculated geometry and inversion barrier energy ''E'' for some C₄H₄MH molecules<ref name=geo>{{cite journal|last1=Pelzer|first1=Silke|last2=Wichmann|first2=Karin|last3=Wesendrup|first3=Ralf|last4=Schwerdtfeger|first4=Peter|title=Trends in Inversion Barriers IV. The Group 15 Analogous of Pyrrole|journal=The Journal of Physical Chemistry A|volume=106|pages=6387–6394|year=2002|issue=26|doi=10.1021/jp0203494|bibcode=2002JPCA..106.6387P }}</ref>

!M !! d(M-C), [[Ångström|Å]]!!d(M-H), Å!!α(C-M-C), °||''E'', kJ/mol

|-

| N || 1.37 ||1.01 ||110||0

|-

| P || 1.81|| 1.425 ||90.5||67

|-

|'''As''' || 1.94|| 1.53 || 86||125

|-

| Sb || 2.14|| 1.725 ||80.5 ||160

|-

| Bi || 2.24 || 1.82 ||78 ||220

|}

Arsole itself has not been isolated experimentally yet, but the molecular geometry and electronic configuration of arsole have been studied theoretically. Calculations also addressed properties of simple arsole derivatives, where hydrogen atoms are substituted by other atoms or small hydrocarbon groups, and there are experimental reports on chemical properties of more complex arsole derivatives. The situation is similar for other C₄H₄MH [[metallole]]s where M = P, As, Sb and Bi.

* [http://www.chm.bris.ac.uk/sillymolecules/sillymols.htm Molecules with silly names]

* [http://dx.doi.org/10.1016/S0022-328X(00)98709-6 Untersuchungen zur Chemie der Arsole] (Studies on the chemistry of arsoles), G. Märkl and H. Hauptmann, ''J. Organomet. Chem.'' '''248''':269 (1983) DOI:10.1016/S0022-328X(00)98709-6

===Planarity===

[[Category:Chemical compounds]]

Calculations suggest that whereas pyrrole (C₄H₄NH) molecule is planar, phosphole (C₄H₄PH) and heavier metalloles are not, and their [[pnictogen]]-bonded hydrogen atom extends out of plane.<ref name=b2>{{cite book|author1=Tadeusz Marek Krygowski|author2=Michal K. Cyrański|author3=M. Agostinha R. Matos|title=Aromaticity in Heterocyclic Compounds|url=https://books.google.com/books?id=_5SOe9RqZAoC&pg=PA47|accessdate=21 March 2011|year=2009|publisher=Springer|isbn=978-3-540-68329-2|pages=47–}}</ref> A similar tendency is predicted for the fluorinated C₄F₄MH derivatives (M = N, P, As, ..), but the inversion barriers are about 50–100% higher. The planarity is lost even in pyrrole when its nitrogen-bonded hydrogen atom is substituted, e.g., with [[fluorine]]. However, the planarity is evaluated in calculation by the energy required to convert between the two configurations where the M-H bond is extending left or right from the molecular plane. However, non-zero (small) value of this energy does not necessarily mean the molecule has low symmetry, because of the possibility of thermal or [[quantum tunneling]] between the two configurations.<ref name=geo/>

===Aromaticity===

[[Aromaticity]] of the arsole manifests itself in [[delocalization]] and [[Resonance (chemistry)|resonance]] of its ring electrons. It is closely related to planarity in that the more planar the molecule the stronger its aromaticity.<ref>{{cite journal|doi=10.1007/s00214-007-0247-0|last1=Pelloni|first1=Stefano|year=2007|pages=89–97|volume=118|journal=Theoretical Chemistry Accounts|last2=Lazzeretti|first2=Paolo|title=Magnetotropicity of phosphole and its arsenic analogue |s2cid=97528113 |hdl=11380/454653|hdl-access=free}}</ref> Aromaticity of arsole and its derivatives has been debated for years both from experimental and theoretical points of view. A 2005 review combined with quantum chemical calculations concluded that arsole itself is "moderately" aromatic as its ring current is 40% that of pyrrole, which is known to be aromatic. However, comparable ring current was calculated for [[cyclopentadiene]], which has long been regarded as non-aromatic.<ref name=rev/> Other reports suggest that the aromaticity (and planarity) can vary between arsole derivatives.<ref name=b2/>

===Chemical properties (arsole derivatives)===

Chemical properties of arsole derivatives have been studied experimentally; they are similar to those of [[phosphole]] and its derivatives.<ref name=b1/> Substitution of all hydrogen atoms in arsole with [[phenyl]] groups yields yellow needles of crystalline '''pentaphenylarsole''', which has a melting point of 215&nbsp;°C. This complex can be prepared, at a yield of 50–93%, by reacting 1,4-diiodo-1,2,3,4-tetraphenylbutadiene<ref>{{cite journal|title=New Unsaturated Heterocyclic Systems. I|last1=Braye|first1=E. H.|last2=Hubel|first2=W.|last3=Caplier|first3=I.|journal=Journal of the American Chemical Society|volume=83|pages=4406–4413|year=1961|issue=21|doi=10.1021/ja01482a026|bibcode=1961JAChS..83.4406B }}</ref> or 1,4-dilithio-1,2,3,4-tetraphenylbutadiene with phenylarsenous dichloride (C₆H₅AsCl₂) in [[ether]].

:[[File:Pentaphenylarsole synthesis.svg|450px]]

Substituting in this reaction [[arsenic trichloride]] for phenylarsenous dichloride yields 1-chloro-2,3,4,5-tetraphenylarsole, which also forms yellow needles but with a lower melting point of 182–184&nbsp;°C. Pentaphenylarsole can further be oxidized with [[hydrogen peroxide]] resulting in yellow crystals with melting point of 252&nbsp;°C. It can also be reacted with [[iron pentacarbonyl]] (Fe(CO)₅) in [[isooctane]] at 150&nbsp;°C to yield a solid organoarsenic compound with the formula C₃₄H₂₅As,Fe(CO)₃.<ref name=b1>{{cite book|first=Frederick&nbsp;George|last=Mann|title=The heterocyclic derivatives of phosphorus, arsenic, antimony, and bismuth|url=https://books.google.com/books?id=OeZ46Zgz2yQC&pg=PA357|accessdate=21 March 2011|year=1970|publisher=John Wiley and Sons|isbn=978-0-471-37489-3|pages=357–360|archive-date=13 June 2014|archive-url=https://web.archive.org/web/20140613004045/http://books.google.com/books?id=OeZ46Zgz2yQC&pg=PA357|url-status=live}}</ref> Reacting pentaphenylarsole with metallic lithium or potassium yields [[1,2,3,4-Tetraphenylnaphthalene|1,2,3-triphenyl naphthalene]].<ref>{{cite book|author1=C. W. Bird|author2=Gordon William Henry Cheeseman|title=Aromatic and Heteroatomic Chemistry|url=https://books.google.com/books?id=wP4O1UCGjlQC&pg=PA23|accessdate=23 March 2011|date=31 December 1973|publisher=Royal Society of Chemistry|isbn=978-0-85186-753-3|pages=23–|archive-date=13 June 2014|archive-url=https://web.archive.org/web/20140613011047/http://books.google.com/books?id=wP4O1UCGjlQC&pg=PA23|url-status=live}}</ref>

Reaction of phenylarsenous dichloride with linear diphenyls results in 1,2,5-triphenylarsole (see below), a solid with a melting point of about 170&nbsp;°C.<ref>{{cite journal|doi=10.1002/anie.197204411|year=1972|author1=Gottfried Märkl|author2=Hagen Hauptmann|name-list-style=amp|pages=441|volume=11|title=Unusual Substitution in an Arsole Ring|journal=Angewandte Chemie International Edition in English|issue=5|url=http://www.chm.bris.ac.uk/sillymolecules/arsole2.pdf|access-date=2011-03-23|archive-date=2011-05-24|archive-url=https://web.archive.org/web/20110524032520/http://www.chm.bris.ac.uk/sillymolecules/arsole2.pdf|url-status=live}}</ref> This compound forms various [[anion]]s upon treatment with alkali metals.<ref>{{cite journal|last1=Märkl|first1=G|title=Synthese von 1-phenyl-2,5-diaryl(dialkyl)-arsolen; umsetzung der arsole mit alkalimetallen und lithiumorganylen|journal=Journal of Organometallic Chemistry|volume=249|pages=335–363|year=1983|issue=2|doi=10.1016/S0022-328X(00)99433-6}}</ref>

:[[File:Substituted arsole.svg|450px]]

==See also==

*[[Pyrrole]], a [[nitrogen]] analog.

*[[Furan]], an [[oxygen]] analog.

*[[Thiophene]], a [[sulfur]] analog.

*[[Simple aromatic rings]]

*[[White spirit|Varsol]], a [[petroleum]] [[Distillation|distillate]] with a [[boiling point|boiling range]] of 150–200&nbsp;°C.

==References==

{{Reflist|2}}

[[Category:Arsenic heterocycles]]

[[Category:Five-membered rings]]