zinc iodide
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477000081
| IUPACName = Zinc iodide
| OtherNames = Zinc(II) iodide
| ImageFile = Portion of ZnI2 lattice (ICD Code2404).png
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 59657
| InChI = 1/2HI.Zn/h2*1H;/q;;+2/p-2
| InChIKey = UAYWVJHJZHQCIE-NUQVWONBAB
| SMILES = I[Zn]I
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/2HI.Zn/h2*1H;/q;;+2/p-2
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = UAYWVJHJZHQCIE-UHFFFAOYSA-L
| CASNo = 10139-47-6
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = 762R7A0O0B
| PubChem = 66278
| RTECS =
}}
|Section2={{Chembox Properties
| Formula = ZnI2
| MolarMass = 319.19 g/mol
| Appearance = white solid
| Density = 4.74 g/cm3
| Solubility = 450 g/100mL (20 °C)
| SolubleOther =
| Solvent =
| MeltingPtC = 446
| BoilingPtC = 1150
| BoilingPt_notes = decomposes
| MagSus = −98.0·10−6 cm3/mol
}}
|Section3={{Chembox Structure
| CrystalStruct = Tetragonal, tI96
| SpaceGroup = I41/acd, No. 142
}}
|Section7={{Chembox Hazards
| ExternalSDS = [http://ptcl.chem.ox.ac.uk/MSDS/ZI/zinc_iodide.html External MSDS]
| HPhrases =
| PPhrases =
| GHS_ref =
| NFPA-H =
| NFPA-F =
| NFPA-R =
| NFPA-S =
| FlashPtC = 625
}}
|Section8={{Chembox Related
| OtherAnions = Zinc fluoride
Zinc chloride
Zinc bromide
| OtherCations = Cadmium iodide
Mercury(I) iodide
| OtherCompounds =
}}
}}
Zinc iodide is the inorganic compound with the formula ZnI2. It exists both in anhydrous form and as a dihydrate. Both are white and readily absorb water from the atmosphere. It has no major application.
Preparation
It can be prepared by the direct reaction of zinc and iodine in water{{cite book|author1=F. Wagenknecht|author2=R. Juza|chapter=Zinc iodide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=1073}}{{cite journal | author = DeMeo, S. | title = Synthesis and Decomposition of Zinc Iodide: Model Reactions for Investigating Chemical Change in the Introductory Laboratory | journal = Journal of Chemical Education | year = 1995 | volume = 72 | issue = 9 | pages = 836 | doi = 10.1021/ed072p836 | bibcode = 1995JChEd..72..836D |url = https://pubs.acs.org/doi/abs/10.1021/ed072p836}} or refluxing ether:{{cite book | author = Eagleson, M. | year = 1994 | title = Concise Encyclopedia Chemistry | url = https://archive.org/details/conciseencyclope00eagl | url-access = registration | publisher = Walter de Gruyter | isbn = 3-11-011451-8 }}
: Zn + I2 → ZnI2
Absent a solvent, the elements do not combine directly at room temperature.{{cite video|first1=George|last1=Gilbert|first2=Kelly|last2=Houston|first3=Jerrold J.|last3=Jacobsen|first4=David|last4=Phillips|orig-date=6 Mar 2012|year=2022|title=Zinc iodine reaction|url=https://www.chemedx.org/video/zinc-iodine-reaction|type=web video|publisher=American Chemical Society, Division of Chemical Education|via=ChemEdX}}
Structure as solid, gas, and in solution
The structure of solid ZnI2 is unusual relative to the dichloride. While zinc centers are tetrahedrally coordinated, as in ZnCl2, groups of four of these tetrahedra share three vertices to form “super-tetrahedra” of composition {Zn4I10}, which are linked by their vertices to form a three-dimensional structure.{{cite book | author = Wells, A. F. | year = 1984 | title = Structural Inorganic Chemistry | edition = 5th | publisher = Oxford Science Publications | isbn = 0-19-855370-6 }} These "super-tetrahedra" are similar to the P4O10 structure.{{cite journal |doi=10.1107/S0567740878010390|title=Structure Cristalline de l'Iodure de Zinc ZnI2|year=1978|last1=Fourcroy|first1=P. H.|last2=Carré|first2=D.|last3=Rivet|first3=J.|journal=Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry|volume=34|issue=11|pages=3160–3162|bibcode=1978AcCrB..34.3160F }}
Molecular ZnI2 is linear as predicted by VSEPR theory with a Zn-I bond length of 238 pm.
In aqueous solution the following have been detected: Zn(H2O)62+, [ZnI(H2O)5]+, tetrahedral ZnI2(H2O)2, ZnI3(H2O)−, and ZnI42−.{{cite journal |author1=Wakita, H. |author2=Johansson, G. |author3=Sandström, M. |author4=Goggin, P. L. |author5=Ohtaki, H. | title = Structure determination of zinc iodide complexes formed in aqueous solution | journal = Journal of Solution Chemistry | year = 1991 | volume = 20 | issue = 7 | pages = 643–668 | doi = 10.1007/BF00650714 |s2cid=97496242 }}
Applications
- Zinc iodide is often used as an x-ray opaque penetrant in industrial radiography to improve the contrast between the damage and intact composite.{{cite book |editor1=Baker, A. |editor2=Dutton, S. |editor3=Kelly, D. | title = Composite Materials for Aircraft Structures | edition = 2nd | year = 2004 | publisher = AIAA (American Institute of Aeronautics & Astronautics) | isbn = 1-56347-540-5 }}{{cite book | title = Plastics Failure Guide | author = Ezrin, M. | publisher = Hanser Gardner Publications | year = 1996 | isbn = 1-56990-184-8 | url = https://books.google.com/books?id=baWyaC3w3hcC }}
- United States patent 4,109,065 {{cite patent | country = US | status = patent | number = 4109065 | title = Rechargeable aqueous zinc-halogen cell | gdate = 1978-08-22 | inventor = Will, F. G.; Secor, F. W. | assign1 = General Electric }} describes a rechargeable aqueous zinc-halogen cell that includes an aqueous electrolytic solution containing a zinc salt selected from the class consisting of zinc bromide, zinc iodide, and mixtures thereof, in both positive and negative electrode compartments.
- In combination with osmium tetroxide, ZnI2 is used as a stain in electron microscopy.{{cite book | author = Hayat, M. A. | title = Principles and Techniques of Electron Microscopy: Biological Applications | year = 2000 | edition = 4th | publisher = Cambridge University Press | isbn = 0-521-63287-0 }}
- As a Lewis acid, zinc iodide catalyzes for the conversion of methanol to triptane and hexamethylbenzene.{{Cite journal|last1=Bercaw|first1=John E.|last2=Diaconescu|first2=Paula L.|author-link2=Paula Diaconescu|last3=Grubbs|first3=Robert H.|last4=Kay|first4=Richard D.|last5=Kitching|first5=Sarah|last6= Labinger|first6=Jay A.|last7=Li|first7=Xingwei|last8=Mehrkhodavandi|first8=Parisa|last9=Morris|first9=George E.|date=2006-11-01|title=On the Mechanism of the Conversion of Methanol to 2,2,3-Trimethylbutane (Triptane) over Zinc Iodide|journal=The Journal of Organic Chemistry|volume=71|issue=23|pages=8907–8917|doi=10.1021/jo0617823|pmid=17081022|issn=0022-3263|url=https://resolver.caltech.edu/CaltechAUTHORS:20170427-090114775 }}
- It can be used as a topical antiseptic.{{citation |last1=Rohe |first1=Dieter M. M. |last2=Wolf |first2=Hans Uwe |contribution=Zinc Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |edition=7th |publisher=Wiley |year=2007 |pages=1–6 |doi=10.1002/14356007.a28_537|title-link=Ullmann's Encyclopedia of Industrial Chemistry |isbn=978-3527306732}}