Benzyl 1226979 223587881 2008-07-04T19:26:52Z Kyle the bot 3115531 robot Adding: [[fr:Benzyl]] [[Image:Benzyl cation.PNG|thumb|100px|right|The structure of a benzyl cation]] In [[organic chemistry]], '''benzyl''' is the term used to describe the [[substituent]] or molecular fragment possessing the structure C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>-. The abbreviation "Bn" is frequently used to denote benzyl moieties in nomenclature and structural depictions of chemical compounds. For example, [[benzyl alcohol]] can be represented as BnOH. This abbreviation is not to be confused with "Bz", which is the abbreviation for the [[benzoyl]] group C<sub>6</sub>H<sub>5</sub>C(O)-. The term '''benzyl''' is also used in reference to the [[carbocation]]<ref>Carey, F. A., and Sundberg, R. J.; ''Advanced Organic Chemistry, Part A: Structure and Mechanisms'', 5th ed.; Springer: New York, NY, 2008. pp 806-808.</ref>, [[anion]], and [[free radical]]<ref>Carey, F. A., and Sundberg, R. J.; ''Advanced Organic Chemistry, Part A: Structure and Mechanisms'', 5th ed.; Springer: New York, NY, 2008. pp 312-313.</ref> moieties featuring a [[benzene]] ring attached to a CH<sub>2</sub> group, in which the CH<sub>2</sub> group bears a positive charge, a negative charge, or a single unpaired electron respectively. In substituent nomenclature, benzyl and [[phenyl]] are commonly confused. Benzyl can be seen as a [[phenyl]] attached to a CH<sub>2</sub> before attaching to the parent compound. ==Benzyl protective groups== Benzyl groups are frequently used in [[organic synthesis]] as [[protective group]] for [[alcohol]]s and [[carboxylic acid]]s. Two common methods for benzyl ether protection: * reaction of alcohol with benzyl bromide and a strong base such as [[sodium hydride]] as in a [[Williamson ether synthesis]]<ref>DeSelms, R. H.; ''[http://www.para-gen.com/paragen/publications.htm Benzyl Phenyl Ether Compounds]''; Enigen Science Publishing: Washington, DC, 2008.</ref> * reaction of alcohol with an [[imidate]] such as '''benzyl trichloroacetimidate''' (C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>OC(CCl<sub>3</sub>)=NH) promoted by [[trifluoromethanesulfonic acid]]. An example forming a p-methoxybenzyl ('''PMB''') ether in total synthesis <ref>''Total synthesis of rutamycin B via Suzuki macrocyclization'' James D. White, Thomas Tiller, Yoshihiro Ohba, Warren J. Porter, Randy W. Jackson, Shan Wang, and Roger Hanselmann 80 [[Chem. Commun.]], 1998 {{DOI|10.1039/a707251a}}</ref>: :[[Image:BenzyletherProtectiveGroup.svg|600px|Benzyl ether protective group White 1998]] The benzyl group can be removed by [[hydrogenation]]. PMB ethers can be cleaved by [[magnesium bromide]] –[[dimethyl sulfide]], [[Ceric ammonium nitrate|CAN]] or [[DDQ]] <ref>''Protecting groups'' Krzysztof Jarowicki and Philip Kocienski [[J. Chem. Soc.]], Perkin Trans. 1, 1998, 4005–4037 '''4005''' {{DOI|10.1039/a803688h}}</ref>. One study <ref>{{cite journal | author = K. W. C. Poon and G. B. Dudley | title = Mix-and-Heat Benzylation of Alcohols Using a Bench-Stable Pyridinium Salt | year = 2006 | journal = [[J. Org. Chem.]] | volume = 71 | issue = 10 | pages = 3923–3927 | doi=10.1021/jo0602773}}</ref> employs a benzyl [[pyridinium salt]] as a benzyl donor for alcohols: :[[Image:Pyridinium salt benzyl ether protection.png|600px|Pyridinium salt benzyl ether protection]] The solvent is trifluoromethylbenzene and [[magnesium oxide]] is an acid scavenger. The reaction type for this conversion is believed to be [[SN1]] based on the detection of trace amounts of [[Friedel-Crafts reaction]] sideproducts with [[toluene]] as a solvent. ==References== <references/> [[Category:Functional groups]] [[Category:protecting groups]] [[de:Benzylgruppe]] [[fr:Benzyl]] [[ja:ベンジル基]] [[pt:Benzil]] [[sv:Bensylgrupp]] [[zh:苄基]]