Diazonium compound: Difference between revisions

{{redirect|Diazo process|the reproduction of prints using the diazo chemical process|Whiteprint}}

[[File:Benzenediazonium cation.png|thumb|150px|right|Benzenediazonium cation.]]

 

===Arenediazonium cations and related species===

According to [[X-ray crystallography]] the {{chem2|C\sN+\tN}} linkage is linear in typical diazonium salts. The {{chem2|N+\tN}} bond distance in [[benzenediazonium tetrafluoroborate]] is 1.083(3) [[Angstrom|Å]],<ref>{{cite journal|doi=10.1139/v82-407|title=The Crystal Structure of Benzenediazonium Tetrafluoroborate, C₆H₅N₂⁺•BF₄⁻1|year=1982|last1=Cygler|first1=Miroslaw|last2=Przybylska|first2=Maria|last3=Elofson|first3=Richard Macleod|journal=Canadian Journal of Chemistry|volume=60|issue=22|pages=2852–2855|doi-access=free}}</ref> which is almost identical to that for dinitrogen molecule (N≡N).

 

 

The stability of arenediazonium salts is highly sensitive to the counterion. Phenyldiazonium chloride is dangerously explosive, but [[benzenediazonium tetrafluoroborate]] is easily handled on the bench.{{Citation needed|date=January 2024}}

 

 

===Alkanediazonium cations and related species===

For secondary and tertiary alkanediazonium species, the enthalpic change is calculated to be close to zero or negative, with minimal activation barrier. Hence, secondary and (especially) tertiary alkanediazonium species are either unbound, nonexistent species or, at best, extremely fleeting intermediates.<ref>{{Cite book|title=Advanced organic chemistry|author=Carey, Francis A.|date=2007|publisher=Springer|others=Sundberg, Richard J.|isbn=9780387448978|edition= 5th|location=New York|oclc=154040953}}</ref>

 

 

== Preparation ==

:{{chem2|ArNH2 + HNO2 + HX → [ArN2]+X- + 2 H2O}}

 

 

:[[File:Preparation of m-trifluoromethylbenzenesulfonyl chloride.svg|500px]]

 

 

:{{chem2|[ArN2]+ + Ar'H → ArN2Ar' + H+}}

 

 

Another commercially important class of coupling partners are acetoacetic amides, as illustrated by the preparation of Pigment Yellow 12, a [[diarylide pigment]].<ref name=Ullmann1>K. Hunger. W. Herbst "Pigments, Organic" in ''Ullmann's Encyclopedia of Industrial Chemistry'', Wiley-VCH, Weinheim, 2012. {{doi|10.1002/14356007.a20_371}}</ref>

:[[Image:PigmentYellow12corrected.png|480px]]

 

<!--The diazo group ({{chem2|N2}}) can be displaced in a process called '''dediazoniation''', which releases nitrogen ({{chem2|N2}}) and an aryl carbocation or more commonly in combination with [[single electron transfer]] an [[aryl radical]].<ref>{{cite journal |title= Radical reactions of arenediazonium ions: An easy entry into the chemistry of the aryl radical |author= Carlo Galli |journal= [[Chem. Rev.]] |doi= 10.1021/cr00087a004 |year= 1988 |volume= 88 |issue= 5 |pages= 765–792}}</ref> Dediazotization is commonly induced by [[halide]]s. The process is a formal [[nucleophilic aromatic substitution]] reaction, is the basis of the [[Sandmeyer Reaction]], the [[Gomberg-Bachmann reaction]] and the [[Schiemann reaction]]. In the so-called '''Craig method''', [[pyridine|2-aminopyridine]] reacts with sodium nitrite, [[hydrobromic acid]] and excess [[bromine]] to 2-bromopyridine.<ref>{{cite journal |title= A Study of the Preparation of Alpha-Pyridyl Halides from Alpha-Aminopyridine by the Diazo Reaction |author= Lyman C. Craig |journal= [[J. Am. Chem. Soc.]] |year= 1934 |volume= 56 |issue= 1 |pages= 231–232 |doi= 10.1021/ja01316a072}}</ref>

[[Image:Craig method.png|300px]]-->

====Sandmeyer reaction====

{{main|Sandmeyer reaction}}

:{{chem2|[C6H5N2]+ + CuCl → C6H5Cl + N2 + Cu+}}

 

|issue= 1 |pages= 1218–1228 |doi= 10.1002/cber.189002301199 |url= http://gallica.bnf.fr/ark:/12148/bpt6k90720c/f1220.chemindefer}}</ref>

:{{chem2|2 Cu + 2 [C6H5N2]+ → 2 Cu+ + (C6H5)2 + 2 N2 (initiation)}}

:{{chem2|[C6H5N2]+ + HX → C6H5X + N2 + H+ (Cu+ catalysis)}}

The traditional Balz–Schiemann reaction has been the subject of many motivations, e.g. using hexafluorophosphate(V) ({{chem2|[PF6]-}}) and hexafluoroantimonate(V) ({{chem2|[SbF6]-}}) in place of tetrafluoroborate ({{chem2|[BF4]-}}). The diazotization can be effected with nitrosonium salts such as nitrosonium hexafluoroantimonate(V) {{chem2|[NO]+[SbF6]-}}.<ref>{{cite journal|journal=Synthesis|year=2010|pages=1804–1821|doi=10.1055/s-0029-1218742|title=C–F Bond Formation for the Synthesis of Aryl Fluorides|first1=Takeru|last1=Furuya|first2=Johannes E. M. N.|last2=Klein|first3=Tobias|last3=Ritter|pmc=2953275|pmid=20953341|volume=2010|issue=11}}</ref>

 

====Replacement by hydrogen====

Arenediazonium cations reduced by [[hypophosphorous acid]],<ref>Reinhard Bruckner, ed. Michael Harmata; Organic Mechanisms Reactions, Stereochemistry and Synthesis 3rd Ed, p.246, {{ISBN|978-3-8274-1579-0}}</ref> [[ethanol]],<ref>{{cite journal|date=1958|title=Mechanisms of Diazonium Salt Reactions. VI. The Reactions of Diazonium Salts with Alcohols under Acidic Conditions; Evidence for Hydride Transfer1|journal=Journal of the American Chemical Society|volume=80|issue=22|pages=6072–6077|doi=10.1021/ja01555a044|last1=DeTarr|first1=D.F.|last2=Kosuge|first2=T.}}</ref> [[sodium stannite]]<ref>Friedlander, Ber., 1889, 587, 22</ref> or alkaline [[sodium thiosulphate]]<ref>Grandmougin, Ber., 1907, 40, 858</ref> gives benzene:

 

==== Replacement by boronate ester group ====

 

:{{chem2|[C6H5N2]+X– + pinB\sBpin → C6H5Bpin + X\sBpin + N2}}

* solvent-induced dediazoniation with [[solvent]] serving as electron donor

 

Benzenediazonium chloride reacts with compounds containing [[activated double bond]]s to produce phenylated products. The reaction is called the [[Meerwein arylation]]:

:{{chem2|[C6H5N2]+Cl- + ArCH\dCH\sCOOH → ArCH\dCH\sC6H5 + N2 + CO2 + HCl}}

 

In their reactions with metal complexes, diazonium cations behave similarly to {{chem2|NO+}}. For example, low-valent metal complexes add with diazonium salts. Illustrative complexes are {{chem2|[Fe(CO)2(PPh3)2(N2Ph)]+}} and the chiral-at-metal complex {{chem2|Fe(CO)(NO)(PPh3)(N2Ph)}}.<ref>{{cite journal |last1= Sutton |first1= D |year= 1993 |title= Organometallic Diazo Compounds |journal= Chem. Rev. |volume= 93 |issue= 3 |pages= 905–1022 |doi= 10.1021/cr00019a008 }}</ref>

 

 

It is also possible to functionalize [[silicon wafer]]s with diazonium salts forming an [[aryl]] monolayer. In one study, the silicon surface is washed with [[ammonium hydrogen fluoride]] leaving it covered with silicon–hydrogen bonds (hydride passivation).<ref>{{Cite journal | title = Direct Covalent Grafting of Conjugated Molecules onto Si, GaAs, and Pd Surfaces from Arenediazonium Salts |author1=Michael P. Stewart |author2=Francisco Maya |author3=Dmitry V. Kosynkin |author4=Shawn M. Dirk |author5=Joshua J. Stapleton |author6=Christine L. McGuiness |author7=David L. Allara |author8=James M. Tour |display-authors=3 |journal= [[J. Am. Chem. Soc.]] |doi= 10.1021/ja0383120 |year= 2004 |volume= 126 |pages= 370–8 |pmid= 14709104 |issue= 1}}</ref> The reaction of the surface with a solution of diazonium salt in [[acetonitrile]] for 2 hours in the dark is a spontaneous process through a [[free radical]] [[reaction mechanism|mechanism]]:<ref>Reaction sequence: silicon surface reaction with [[ammonium hydrogen fluoride]] creates [[hydride]] layer. An electron is transferred from the silicon surface to the diazonium salt in an [[open circuit potential]] reduction leaving a silicon [[radical cation]] and a diazonium radical. In the next step a proton and a nitrogen molecule are expelled and the two radical residues recombine creating a surface silicon to carbon bond.</ref>

So far grafting of diazonium salts on metals has been accomplished on [[iron]], [[cobalt]], [[nickel]], [[platinum]], [[palladium]], [[zinc]], [[copper]] and [[gold]] surfaces.<ref>{{Cite journal|last1=Bélanger|first1=Daniel|last2=Pinson|first2=Jean|date=2011|title=Electrografting: a powerful method for surface modification|url=http://xlink.rsc.org/?DOI=c0cs00149j|journal=Chemical Society Reviews|language=en|volume=40|issue=7|pages=3995–4048|doi=10.1039/c0cs00149j|pmid=21503288|issn=0306-0012}}</ref> Also grafting to diamond surfaces has been reported.<ref>{{cite journal | title = Chemical Grafting of Biphenyl Self-Assembled Monolayers on Ultrananocrystalline Diamond |author1=S.Q. Lud |author2=M. Steenackers |author3=P. Bruno |author4=D.M. Gruen |author5=P. Feulner |author6=J.A. Garrido |author7=M. Stutzmann |display-authors=3 |journal= [[J. Am. Chem. Soc.]] |doi= 10.1021/ja0657049 |year= 2006 |volume= 128 |pages= 16884–91 |pmid= 17177439 |issue= 51}}</ref> One interesting question raised is the actual positioning on the aryl group on the surface. An [[in silico]] study <ref>{{cite journal |title= Structure and Bonding between an Aryl Group and Metal Surfaces |author1=De-en Jiang |author2=Bobby G. Sumpter |author3=Sheng Dai |journal= [[J. Am. Chem. Soc.]] |doi= 10.1021/ja061439f |year= 2006 |volume= 128 |pages= 6030–1 |pmid= 16669660 |issue= 18|s2cid=41590197 }}</ref> demonstrates that in the [[period 4 element]]s from titanium to copper the [[binding energy]] decreases from left to right because the number of d-electrons increases. The metals to the left of iron are positioned tilted towards or flat on the surface favoring metal to carbon [[pi bond]] formation and those on the right of iron are positioned in an upright position, favoring metal to carbon [[sigma bond]] formation. This also explains why diazonium salt grafting thus far has been possible with those metals to right of iron in the [[periodic table]].

 

Diazonium salts can be reduced with [[stannous chloride]] ({{chem2|SnCl2}}) to the corresponding [[hydrazine]] derivatives. This reaction is particularly useful in the [[Fischer indole synthesis]] of [[triptan]] compounds and [[indometacin]]. The use of [[sodium dithionite]] is an improvement over stannous chloride since it is a cheaper reducing agent with fewer environmental problems.

 

== External links ==

* {{cite web |publisher= [[Michigan State University]] |author= W. Reusch |work= VirtualText of Organic Chemistry |title= Reactions of Amines |url= http://www.cem.msu.edu/~reusch/VirtualText/amine2.htm |url-status= dead |archive-url= https://archive.today/20121212131033/http://www.cem.msu.edu/~reusch/VirtualText/amine2.htm |archive-date= 2012-12-12 }}

[[Category:Organic compounds]]

[[Category:Carbon-heteroatom bond forming reactions]]