[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"detail-sidebar-cat-0-en-105":3,"doc-seo-657086-105":59,"doc-detail-657086-en":130},{"code":4,"msg":5,"data":6},0,"success",[7,13,18,23,28,33,38,43,48,51,55],{"id":8,"doc_module":4,"doc_module_name":9,"category_name":10,"show_sort_weight":11,"slug":12},1,"Document","Story & Novel",90,"story-novel",{"id":14,"doc_module":4,"doc_module_name":9,"category_name":15,"show_sort_weight":16,"slug":17},2,"Literature",80,"literature",{"id":19,"doc_module":4,"doc_module_name":9,"category_name":20,"show_sort_weight":21,"slug":22},4,"Exam",70,"exam",{"id":24,"doc_module":4,"doc_module_name":9,"category_name":25,"show_sort_weight":26,"slug":27},5,"Comic",60,"comic",{"id":29,"doc_module":4,"doc_module_name":9,"category_name":30,"show_sort_weight":31,"slug":32},6,"Technology",50,"technology",{"id":34,"doc_module":4,"doc_module_name":9,"category_name":35,"show_sort_weight":36,"slug":37},7,"Healthcare",40,"healthcare",{"id":39,"doc_module":4,"doc_module_name":9,"category_name":40,"show_sort_weight":41,"slug":42},8,"Research & Report",30,"research-report",{"id":44,"doc_module":4,"doc_module_name":9,"category_name":45,"show_sort_weight":46,"slug":47},9,"Religion & Spirituality",20,"religion-spirituality",{"id":46,"doc_module":4,"doc_module_name":9,"category_name":49,"show_sort_weight":46,"slug":50},"World Cup","world-cup",{"id":52,"doc_module":4,"doc_module_name":9,"category_name":53,"show_sort_weight":52,"slug":54},10,"Lifestyle","lifestyle",{"id":56,"doc_module":4,"doc_module_name":9,"category_name":57,"show_sort_weight":24,"slug":58},19,"General","general",{"code":4,"msg":60,"data":61},"ok",{"site_id":62,"language":63,"slug":64,"title":65,"keywords":66,"description":67,"schema_data":68,"social_meta":123,"head_meta":125,"extra_data":127,"updated_unix":129},105,"en","chem95002-orbitals-in-organic-chemistry-pericyclics-lecture-5-introduction-to-pericyclic-reactivity-i","CHEM95002 Orbitals in Organic Chemistry - Pericyclics Lecture 5 - Introduction to Pericyclic Reactivity I","","Lecture 5 introduces pericyclic reactivity in organic chemistry, covering the defining “in concert on a closed curve” bonding changes and the role of cyclic transition states with reorganisation of σ and π systems. It surveys major pericyclic reaction types—cycloadditions, group transfer, sigmatropic rearrangements, and electrocyclic reactions—contrasting ionic SN1/SN2 mechanisms. The lecture also explains how to draw molecular orbitals for conjugated p-systems via the FMO approach and uses symmetry correlation/orbital correlation diagrams for Diels–Alder and [2+2] examples.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/chem95002-orbitals-in-organic-chemistry-pericyclics-lecture-5-introduction-to-pericyclic-reactivity-i/657086/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/chem95002-orbitals-in-organic-chemistry-pericyclics-lecture-5-introduction-to-pericyclic-reactivity-i/657086.png","ImageObject",300,407,{"name":92,"@type":93},"EvelynWrites","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-29","2026-10-26",true,{"@type":102,"interactionType":103,"userInteractionCount":81},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What makes a reaction “pericyclic” rather than stepwise or ionic?","Question",{"text":112,"@type":113},"Pericyclic reactions are “no-mechanism” thermoreorganisation processes such as Diels–Alder and Claisen/Cope rearrangements, where the key explanation is the concerted transition-state reorganisation rather than a step-by-step pathway.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How do the four classes of pericyclic reactions differ?",{"text":117,"@type":113},"Cycloadditions are typically between two components, while sigmatropic rearrangements and electrocyclic reactions are unimolecular (sigmatropic) or involve ring closure/opening from a conjugated system (electrocyclic).",{"name":119,"@type":110,"acceptedAnswer":120},"What steps are taught for drawing molecular orbitals using the FMO approach?",{"text":121,"@type":113},"Count the number of p-orbitals, count electrons based on π bonds and charge (e.g., unpaired electrons, carbanion/carbo cation rules), draw stacked horizontal lines for the MOs, then combine p-orbitals with increasing nodes. The terminal orbital phases follow node parity, enabling construction of HOMO/LUMO structures and correlation diagrams.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},657086,1793025565,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":81,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":139,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":144,"read_time":41},687212989558,"https://ap-avatar.wpscdn.com/davatar_a8503ba1806abce46bf441b54a3ca4cd","1  \nCHEM95002:  \nOrbitals in Organic Chemistry– Pericyclics LECTURE 5 Introduction to Pericyclic Reactivity I  \nAlan C. Spivey  \n[a.c.spivey@imperial.ac.uk](a.c.spivey@imperial.ac.uk)  \nMar 2020  \n2  \nFormat & scope of lecture 5  \n• The nature of pericyclic reactions  \n• Types of pericyclic reactions  \n– Cycloadditions  \n– Group Transfer reactions  \n– Sigmatropic rearrangements  \n– Electrocyclic reactions  \n• Drawing molecular orbitals for conjugated p-systems  \n– FMO approach  \n• Symmetry correlation diagrams  \n– Diels-Alder reaction (a thermal reaction)  \n– [2+2]-cycloaddition (a photochemical reaction)  \n3  \n• Ionic reactions (e.g. SN 1 and SN2 r  an intermediate  \nMe  MeX Me  \nMe  \nMe  \nMe  \nMe MeNu Me  \nSN 1 reactions are stepwise & have a defined intermediate  \nMeX Me  \nMe MeNu  \nMe  \nMe  N~~u ~~ + HI  \nEt  \nMe  \n(-)  (-)  \nNu  I  \nEt H  \n‡  \nMe NuH + I  \nEt  \nSN 2 reactions are concerted & have no intermediate  \n‡  \n• In ionic reactions the curly arrows identify where the electrons have come from and where they are going and which bonds have been made and which broken  \nPericyclic reactions 4  \n• Pericyclic reactions are those ‘in which all first-order changes in bonding relationships take place in concert on a closed curve’(Woodward and Hoffmann, 1969)  \n• This means that the reactions have cyclic transition states in which all bond-forming and bondbreaking take place in a concerted manner without the formation of an intermediate  \n• Reactions involve a transition state with a cyclic array of interacting orbitals; a reorganisation of σ and π-bonds occurs within this cyclic array  \nO  \nO  \nO  \nor  \nO  \nO  \nO  \nO  \nO  \nO  \nH  \nH  \n• There is no absolute sense in which the electrons flow from one component to another (but it is sometimes more sensible to push the arrows in one direction than the other). This means that the arrows demonstrate which bonds are being broken and made rather than the ‘flow’ of electrons’  \nPericyclic reactions 5  \n‘“No-mechanism” is the designation given, half in jest, half in desperation, to ‘thermoreorganization’ reactions like the Diels-Alder and the Claisen and Cope rearrangements’*  \n• Observations that required an explanation, e.g.:  \n– The [4+2](Diels Alder) reaction occurs thermally, whereas the [2+2] reaction does not  \nO O    \nO   O       \nO O    \n– Heating or irradiating hexatrienes leads to different stereochemistry  \n  hn    heat    \n*Doering, Tetrahedron, 1962 , 18 , 67 [ DOI]  \nFour classes of pericyclic reactions  \n\n| 1. Cycloaddition reactions |\n| --- |\n| Two components come together to form two new σ-bonds at the ends of both components and joining them together to form a ring. |\n\n\n| 2. Group transfer reactions |\n| --- |\n| A mix of a sigmatropic rearrangement and a cycloaddition. Bimolecular, so not sigmatropic rearrangements, and no ring is formed so they are not cycloadditions. |\n\n6  \nDiels-Alder reaction  \nO  \nO  \nO  \n1,3-Dipolar cycloaddition  \nMeO    \nN~~ ~~Me  \nCheletropic extrusion  \nO  \nO  \nO  \nO  \nMeO  \nN~~ ~~Me  \n+  \nCO  \nAlder-ene reaction  \nSyn-elimination reaction  \nDiimide reduction  \nN ~~ ~~ N  \nH H  \nH  \nO  \nO  \nO  \nPh ~~ ~~ OSe H  \nN N  \nH H  \nFour classes of pericyclic reactions 7  \n3. Sigmatropic rearrangements  \nUnimolecular isomerisations which formally involve the overall movement of a σ-bond from one position to another.  \n\n| 4. Electrocyclic reactions |\n| --- |\n| Unimolecular reactions characterized by the formation of a ring from an open chain conjugated system with a σ-bond forming across the ends of the conjugated system. |\n\nCope rearrangement  \n3 2 1   \n[3,3]  \n3 2 1  \nClaisen rearrangement  \n3 2 1  \nO  \n3 2 1  \n[3,3]  \n[1,5]-hydride shift  \n5  \n4  \n1  \nH  \n3  \n1  \n2  \n[1,5]  \nH  \nHexatriene electrocyclic ring-closure  \nCyclobutene electrocyclic ring-opening  \n8  \n◼ To draw Da ml MdiaOgrami-on: tifying FMOs  \ni) count the number of p-orbitals: n  \nii) count the number of electrons: π-bond = 2, unpaired electron = 1, carbanion = 2, carbocation = 0  \n","cbCaioFORKRqJtH6","https://ap.wps.com/l/cbCaioFORKRqJtH6","pdf",1763938,12,"English","# Format & scope of lecture 5\n## The nature of pericyclic reactions\n## Types of pericyclic reactions\n## Drawing molecular orbitals for conjugated p-systems (FMO)\n## Symmetry correlation diagrams\n# Ionic reactions (SN1 and SN2)\n# Four classes of pericyclic reactions\n## Cycloaddition reactions\n## Group transfer reactions\n## Sigmatropic rearrangements\n## Electrocyclic reactions\n# Orbital correlation diagrams","[{\"question\":\"What makes a reaction “pericyclic” rather than stepwise or ionic?\",\"answer\":\"Pericyclic reactions are “no-mechanism” thermoreorganisation processes such as Diels–Alder and Claisen/Cope rearrangements, where the key explanation is the concerted transition-state reorganisation rather than a step-by-step pathway.\"},{\"question\":\"How do the four classes of pericyclic reactions differ?\",\"answer\":\"Cycloadditions are typically between two components, while sigmatropic rearrangements and electrocyclic reactions are unimolecular (sigmatropic) or involve ring closure/opening from a conjugated system (electrocyclic).\"},{\"question\":\"What steps are taught for drawing molecular orbitals using the FMO approach?\",\"answer\":\"Count the number of p-orbitals, count electrons based on π bonds and charge (e.g., unpaired electrons, carbanion/carbo cation rules), draw stacked horizontal lines for the MOs, then combine p-orbitals with increasing nodes. The terminal orbital phases follow node parity, enabling construction of HOMO/LUMO structures and correlation diagrams.\"}]","CHEM95002 Orbitals in Organic Chemistry - Pericyclics Lecture 5 - Introduction to Pericyclic Reactivity I | PDF",1792973614]