the-french-artist/wikipedia_20220301.simple_sentence_embeddings huggingface dataset:
Pericyclic reaction 
 However, it is possible to push the reaction in one direction if the product is at a significantly lower energy level.
Pericyclic reaction 
 For example, it is not definitively known whether the [2+2] cycloaddition mechanism is concerted (or may depend on the reactive system).
Pericyclic reaction 
 A large photoinduced hydrogen sigmatropic shift was utilized in a corrin synthesis performed by Albert Eschenmoser containing a 16π system.
Pericyclic reaction 
 Due to the principle of microscopic reversibility, there is a parallel set of "retro" pericyclic reactions, which perform the reverse reaction.
Pericyclic reaction 
 non-enzymatic, photochemical electrocyclic ring opening and a (1,7) sigmatropic hydride shift in vitamin D synthesis.
Pericyclic reaction 
 a conversion of Isochorismate into salicylate and Pyruvate in a catalyzed, true pericyclic reaction.
The Annoying Orange 
 The episodes are uploaded to the YouTube channel realannoyingorange weekly, with now over 200 videos. ,
The Annoying Orange 
 He was Orange (Annoying Orange)'s best friend and normally tells Orange to stop being annoying and shut up, but it is discovered in the episode "Wishful Thinking" that Pear would not be friends without Grapefruit.
The Annoying Orange 
 In 2012, Cartoon Network made a 2012-2014 high fructose adventures TV show based on the YouTube series.
Cycloaddition 
 A cycloaddition is a chemical reaction between reactants with double bonds that get replaced by a ring structure.
Cycloaddition 
 It is a pericyclic chemical reaction where "two or more unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity."
Cycloaddition 
 This would make the Diels–Alder reaction a [4 + 2]cycloaddition, and the 1,3-dipolar cycloaddition a [3 + 2]cycloaddition.
Cycloaddition 
 Thermal cycloadditions usually have (4n + 2) π electrons participating in the starting material, for some whole number n.  Because of orbital symmetry, most cycloadditions are suprafacial-suprafacial.
Cycloaddition 
 There are a few examples of thermal cycloadditions which have 4n π electrons (for example the [2 + 2] cycloaddition).
Cycloaddition 
 Cycloadditions in which 4n π electrons participate can also occur as a result of photochemical activation.
Cycloaddition 
 Here, one component makes an electron move from the  highest occupied molecular orbital (HOMO) (π bonding) to the lowest unoccupied molecular orbital (LUMO) (π* antibonding).
Cycloaddition 
 After the electron is promoted to the higher orbital, orbital symmetry allows the reaction to proceed in a suprafacial-suprafacial manner.
Cycloaddition 
 Note that not all photochemical (2+2) cyclizations are cycloadditions; some are known to operate by radical mechanisms.
Cycloaddition 
 Some cycloadditions instead of π bonds operate through strained cyclopropane rings; as these have significant π character.
Cycloaddition 
 In the (i+j+...) cycloaddition notation i and j refer to the number of atoms involved in the cycloaddition.
Cycloaddition 
 In this notation a Diels-Alder reaction is a (4+2)cycloaddition and a 1,3-dipolar addition such as the first step in ozonolysis is a (3+2)cycloaddition.
Cycloaddition 
 In this notation, the Diels–Alder reaction and the dipolar reaction both become a [4+2]cycloaddition.
Cycloaddition 
 Cycloadditions often have metal-catalyzed and stepwise radical analogs, however these are not strictly speaking pericyclic reactions.
Cycloaddition 
 When charged or radical intermediates are involved in a cycloaddition, or when the cycloaddition result is found in a series of reaction steps, they are sometimes called formal cycloadditions to make a difference from true pericyclic cycloadditions.
Cycloaddition 
 One example of a formal [3+3]cycloaddition between a cyclic enone and an enamine catalyzed by n-butyllithium is a Stork enamine / 1,2-addition cascade reaction:
Cheletropic reaction 
 A cheletropic reaction is a type of pericyclic reaction where one atom on one of the reagents gets two new bonds.
Cheletropic reaction 
 A pericyclic reaction is one that involves a transition state with a cyclic array of atoms and an associated cyclic array of interacting orbitals.
Cheletropic reaction 
 What sets cheletropic reactions apart is that on one of the reagents, both new bonds are being made to the same atom.<ref name="Fleming">Ian Fleming.
Cheletropic reaction 
 The first two examples are known as "cheletropic extrusions" because a small stable molecule is given off in the reaction.
Cheletropic reaction 
 The driving force for these reactions is often the entropic benefit of releasing a gas (e.g. CO or N2).
Cheletropic reaction 
 Because of the geometry of the molecules involved in cheletropic reactions, they confirm a number of predictions made by theoretical chemists.
Cheletropic reaction 
 In the linear approach, the electrons in the orbital of the small molecule are pointed directly at the π system of the big molecule.
Cheletropic reaction 
 A diagram of a two-electron fragment approaching a four-electron π-system using frontier molecular orbitals is shown below.
Cheletropic reaction 
 The rotation will be disrotatory if the small molecule approaches linearly and conrotatory if the molecule approaches non-linearly.
Cheletropic reaction 
 If aromatic, linear approaches use disrotatory motion while non-linear approaches use conrotatory motion.
Cheletropic reaction 
 Linear approaches will have conrotatory motion while non-linear approaches will have disrotatory motion.
Cheletropic reaction 
 The kinetic product comes from a Diels–Alder reaction, while a cheletropic reaction makes a more thermodynamically stable product.
Cheletropic reaction 
 The path to the left shows the thermodynamic product, while the path to the right shows the kinetic product.
Cheletropic reaction 
 Monnat, Vogel, and Sordo, in 2002, measured the kinetics of addition of sulfur dioxide to 1,2-dimethylidenecycloalkanes.
Cheletropic reaction 
 They wrote that the reaction of 1,2-dimethylidenecyclohexane with sulfur dioxide can give two different products depending on reaction conditions.
Cheletropic reaction 
 The reaction makes the corresponding sultine through a hetero-Diels-Alder reaction under kinetic control (≤ -60 °C), but, under thermodynamic control (≥ -40 °C), the reaction makes the corresponding sulfolene through a cheletropic reaction.
Cheletropic reaction 
 The activation enthalpy for the hetero-Diels-Alder reaction is about 2 kcal/mol smaller than that for the corresponding cheletropic reaction.
Cheletropic reaction 
 Similar results were found in an 1995 study by Suarez, Sordo, and Sordo which used ab initio calculations to study the kinetic and thermodynamic control of the reaction of sulfur dioxide with 1,3-dienes.
Cheletropic reaction 
 The effect of the solvent of the cheletropic reaction of 3,4-dimethyl-2,5-dihydrothiophen-1,1-dioxide (shown at right) was kinetically investigated in 14 solvents.
Cheletropic reaction 
 The reaction rate constants of the forward and reverse reaction in addition to the equilibrium constants were found to be linearly correlated with the ET(30) solvent polarity scale.
Cheletropic reaction 
 The reverse rate k-1 was found to increase by a factor of 53 going from cyclohexane to methanol, while the equilibrium constant Keq decreased by a factor of 140.
Cheletropic reaction 
 It is suggested that there is a change of the polarity during the activation process as evidenced by relationships between the equilibrium and kinetic data.
Cheletropic reaction 
 The authors say that the reaction appears to be influenced by the polarity of the solvent, and this can be shown by the change in the dipole moments when going from reactant to transition state to product.
Cheletropic reaction 
 The authors also state that the cheletropic reaction doesn’t seem to be influenced by either solvent acidity or basicity.
Cheletropic reaction 
 The rate constants will be characterized by opposite effect on the polarity: k1 will slightly decrease with the increase of ET(30), and k-1 will increase under the same conditions.
Cheletropic reaction 
 One of the most synthetically important cheletropic reactions is the addition of a singlet carbene to an alkene to make a cyclopropane (see figure at left).
Cheletropic reaction 
 A carbene is a neutral molecule containing a divalent carbon with six electrons in its valence shell.
Cheletropic reaction 
 Because of this, carbenes are highly reactive electrophiles and generated as reaction intermediates.
Cheletropic reaction 
 Interaction of the filled carbene orbital with the alkene π system creates a four-electron system and favors a non-linear approach.
Cheletropic reaction 
 However, while theory clearly favors a non-linear approach, there are no obvious experimental implications for a linear vs. non-linear approach.
Sigmatropic reaction 
 A sigmatropic reaction does not use a catalyst and involves a single molecule (an uncatalyzed intramolecular process).
Sigmatropic reaction 
 The name sigmatropic is the result of a compounding of the long-established "sigma" name for single carbon-carbon bonds and the Greek word tropos, meaning turn.
Sigmatropic reaction 
 This is a rearrangement reaction which means that the bonds in a molecule shift between atoms without any atoms leaving or new atoms added to the molecule.
Sigmatropic reaction 
 In a sigmatropic reaction, a substituent moves from one part of a π-bonded system to another part in an intramolecular reaction with simultaneous rearrangement of the π system.
Sigmatropic reaction 
 Sigmatropic reactions often have transition-metal catalysts that form intermediates in analogous reactions.
Sigmatropic reaction 
 The most well-known of the sigmatropic rearrangements are the [3,3] Cope rearrangement, Claisen rearrangement, Carroll rearrangement and the Fischer indole synthesis.
Sigmatropic reaction 
 This means the migration of a σ-bond adjacent to one or more π systems to a new position (i-1) and (j-1) atoms removed from the original location of the σ-bond.
Sigmatropic reaction 
 When the sum of i and j is an even number, this is an indication of the involvement of a neutral, all C atom chain.
Sigmatropic reaction 
 An odd number suggests that there is a charged C atom or of a heteroatom lone pair replacing a carbon-carbon double bond.
Sigmatropic reaction 
 Thus, [1,5] and [3,3] shifts become [1,4] and [2,3] shifts with heteroatoms, while preserving symmetry considerations.
Sigmatropic reaction 
 The first step is to give numbers to each atom starting with the atoms of the bond being broken as atom 1.
Sigmatropic reaction 
 Chemists count the atoms in each direction from the broken bond to the atoms that form the new σ-bond in the product.
Sigmatropic reaction 
 The numbers that correspond to the atoms forming the new bond are then separated by a comma and placed within brackets.
Sigmatropic reaction 
 So, chemists count across all atoms involved in the reaction rather than only across the closest atoms.
Sigmatropic reaction 
 For example, the following hydrogen atom migration is of order [1,5], attained by counting counterclockwise through the π system, rather than the [1,3] order through the ring CH2 group that would mistakenly result if counted clockwise.
Sigmatropic reaction 
 In principle, all sigmatropic shifts can occur with either the same (retention) or the opposite (inversion) geometry of the migrating group.
Sigmatropic reaction 
 This depends on whether the original bonding lobe of the migrating atom or its other lobe is used to form the new bond.
Sigmatropic reaction 
 In cases of stereochemical retention, the migrating group translates without rotation into the bonding position.
Sigmatropic reaction 
 In the case of stereochemical inversion the migrating group both rotates and translates to reach its bonded conformation.
Sigmatropic reaction 
 There is another way that a sigmatropic reaction can produce products with different sterochemistry.
Sigmatropic reaction 
 Although such a shift is symmetry allowed, the Mobius topology required in the transition state prohibits such a shift.
Sigmatropic reaction 
 But an alkyl group, due to the nature of its orbitals, can invert its geometry and form a new bond with the back lobe of its sp3 orbital.
Sigmatropic reaction 
 These reactions are still not common in open chain systems because of the highly ordered nature of the transition state.
Sigmatropic reaction 
 Photochemical [1,3] shifts should be suprafacial shifts; however, most are non-concerted because they proceed through a triplet state (that is, they have a diradical mechanism, to which the Woodward-Hoffmann rules do not apply).
Sigmatropic reaction 
 Hydrogen has been shown to shift in both cyclic and open chain systems at temperatures at or above 200 ˚C. These reactions are predicted to proceed suprafacially, by a Huckel-topology transition state.
Sigmatropic reaction 
 In contrast to hydrogen [1,5] shifts, there have never been any observed [1,5] alky shifts in an open-chain system.
Sigmatropic reaction 
 Chemists have determined rate preferences for [1,5] alkyl shifts in cyclic systems:  carbonyl and carboxyl> hydride> phenyl and vinyl>> alkyl.
Sigmatropic reaction 
 However, for cyclohexadienes, the temperature for alkyl shifts is not much higher than that for carbonyls, the best migratory group.
Sigmatropic reaction 
 A study showed that this is because alkyl shifts on cyclohexadienes proceed through a different mechanism.
Sigmatropic reaction 
 This same mechanistic process is seen below, without the final electrocyclic ring-closing reaction, in the interconversion of lumisterol to vitamin D2.
Sigmatropic reaction 
 [1,7] sigmatropic shifts are predicted by the Woodward-Hoffmann rules to proceed in an antarafacial fashion, by a Mobius topology transition state.
Sigmatropic reaction 
 An antarafacial [1,7] shift is observed in the conversion of lumisterol to vitamin D2, where following an electrocyclic ring opening to previtamin D2, a methyl hydrogen shifts.
Sigmatropic reaction 
 Bicyclic nonatrienes also undergo [1,7] shifts in a so called walk rearrangement, which is the shift of divalent group, as part of a three-membered ring, in a bicyclic molecule.
Sigmatropic reaction 
 The Woodward-Hoffman rules predict that these six electron reactions would proceed suprafacially, using a Huckel topology transition state.
Sigmatropic reaction 
 Discovered in 1912 by Rainer Ludwig Claisen, the Claisen rearrangement is the first recorded example of a [3,3]-sigmatropic rearrangement.
Sigmatropic reaction 
 An example of Claisen rearrangement is the [3,3] rearrangement of an allyl vinyl ether, which upon heating yields a γ,δ-unsaturated carbonyl.
Sigmatropic reaction 
 The formation of a carbonyl group makes this reaction, unlike other sigmatropic rearrangements, inherently irreversible.
Sigmatropic reaction 
 The ortho-Claisen rearrangement involves the [3,3] shift of an allyl phenyl ether to an intermediate which quickly tautomerizes to an ortho-substituted phenol.
Sigmatropic reaction 
 When both the ortho positions on the benzene ring are blocked, a second ortho-Claisen rearrangement will occur.
Sigmatropic reaction 
 The Cope rearrangement is an extensively studied organic reaction involving the [3,3] sigmatropic rearrangement of 1,5-dienes.
Sigmatropic reaction 
 The Oxy-Cope rearrangement a hydroxyl group is added at C3 forming an enal or enone after Keto-enol tautomerism of the intermediate enol:
Sigmatropic reaction 
 The Carroll rearrangement is a rearrangement reaction in organic chemistry and involves the transformation of a β-keto allyl ester into a α-allyl-β-ketocarboxylic acid.
Sigmatropic reaction 
 This organic reaction can be followed by decarboxylation and the final product is a γ,δ-allylketone.
Sigmatropic reaction 
 The Carroll rearrangement is an adaptation of the Claisen rearrangement and effectively a decarboxylative allylation.
Sigmatropic reaction 
 The Fischer indole synthesis is a chemical reaction that produces the aromatic heterocycle indole from a (substituted) phenylhydrazine and an aldehyde or ketone under acidic conditions.
Sigmatropic reaction 
 Successful acid catalysts include: Bronsted acids such as HCl, H2SO4, polyphosphoric acid and p-toluenesulfonic acid.
Sigmatropic reaction 
 Lewis acids such as boron trifluoride, zinc chloride, iron chloride, and aluminium chloride are also useful catalysts.
Sigmatropic reaction 
 Similar to [3,3] shifts, the Woodward-Hoffman rules predict that [5,5] sigmatropic shifts would proceed suprafacially, Huckel topology transition state.
Sigmatropic reaction 
 These reactions are rarer than [3,3] sigmatropic shifts, but this is mainly a function of the fact that molecules that can undergo [5,5] shifts are rarer than molecules that can undergo [3,3] shifts.
Sigmatropic reaction 
 The migration of a divalent group, such as O, S, NR or CR2, which is part of a three-membered ring in a bicyclic molecule, is commonly referred to as a walk rearrangement.
Sigmatropic reaction 
 This can be formally characterized according to the Woodward-Hofmann rules as being a (1, n) sigmatropic shift.
Sigmatropic reaction 
 An example of such a rearrangement is the shift of substituents on tropilidenes (1,3,5-cycloheptatrienes).
Sigmatropic reaction 
 When heated, the pi-system goes through an electrocyclic ring closing to form bicycle[4,1,0]heptadiene (norcaradiene).
Sigmatropic reaction 
 Proceeding through a [1,5] shift, the walk rearrangement of norcaradienes is expected to proceed suprafacially with a retention of stereochemistry.
Sigmatropic reaction 
 Experimental observations, however, show that the 1,5-shifts of norcaradienes proceed antarafacially.
Sigmatropic reaction 
 Theoretical calculations found the [1,5] shift to be a diradical process, but without involving any diradical minima on the potential energy surface.
Group transfer reaction 
 A Group transfer reaction is pericyclic reaction where one pi bond is converted to one sigma bond, at the same time that a sigma bond migrates.
Cadel Evans 
 Cadel Evans (born 14 February 1977 in Katherine, Northern Territory) is an Australian professional bicycle race driver.
Cadel Evans 
 Cadel Evans was born on 14 February 1977 at the Katherine Hospital, Katherine, Northern Territory, Australia.
Cadel Evans 
 His father describes him as a good student, but otherwise just an ordinary kid who would leave his toys around. "
Grand Army Plaza (Manhattan) 
 The northern part has a golden statue of William Tecumseh Sherman designed by Augustus Saint-Gaudens.
USS Enterprise (CV-6) 
 USS Enterprise (CV-6), often called the "Big E," was the sixth aircraft carrier of the United States Navy.
USS Enterprise (CV-6) 
 She was one of three American carriers brought into service before World War II which survived the war.
USS Enterprise (CV-6) 
 These fights included the Battle of Midway, the Battle of the Eastern Solomons, the Battle of the Santa Cruz Islands, many other fights during the Guadalcanal campaign, the Battle of the Philippine Sea, and the Battle of Leyte Gulf.
USS Enterprise (CV-6) 
 At three different times during the Pacific War, the Japanese said that she had been sunk in battle.
USS Enterprise (CV-6) 
 Some have said that she is the most glorious and honored ship in the history of the United States Navy.
USS Enterprise (CV-6) 
 She was sponsored by Lulie Swanson, who was the wife of the Secretary of the Navy Claude A. Swanson.
USS Enterprise (CV-6) 
 She was first based in San Diego (where she was used in the movie Dive Bomber) and then at Pearl Harbor after President Roosevelt ordered the Fleet to be based far forward.
USS Enterprise (CV-6) 
 Enterprise and the aircraft squads she carries trained a lot and moved aircraft among the island bases of the Pacific.
USS Enterprise (CV-6) 
 Enterprise was completing a transport mission, returning to Hawaii after moving Marine Fighter Squadron 211 (VMF-211) to Wake Island on 7 December 1941.
USS Enterprise (CV-6) 
 18 SBD Dauntlesses from Enterprise squadrons Scouting Squadron Six (VS-6) and Bombing Squadron Six (VB-6) arrived at Pearl Harbor while the Japanese were attacking it.
USS Enterprise (CV-6) 
 During the battle, one radio report was heard: "Do not attack me, this is Six Baker Three an American plane".
USS Enterprise (CV-6) 
 Later, the same pilot (Ensign Manuel Gonzales from VB-6) was heard telling his radioman/gunner to get ready to land on the water.
USS Enterprise (CV-6) 
 Lieutenant C. E. Dickinson and his crewmate William C. Miller, from VS-6, shot down one Japanese plane before they had to jump out after their plane caught fire.
USS Enterprise (CV-6) 
 All of these aircraft except two were shot down by shellshocked AA gunners when they tried to land on Ford Island later that night.
USS Enterprise (CV-6) 
 Enterprise got her aircraft ready to go on a large search for the Japanese force that attacked Pearl Harbor.
USS Enterprise (CV-6) 
 Early the next morning, she went to patrol the rest of the Hawaiian Islands to make sure there were no more attacks.
USS Enterprise (CV-6) 
 During the last two weeks of December 1941, Enterprise and her group moved to the west of Hawaii to make sure those islands were not attacked.
USS Enterprise (CV-6) 
 On 1 February, Enterprise'''s Task Force 8 raided Kwajalein, Wotje, and Maloelap in the Marshall Islands.
USS Enterprise (CV-6) 
 Five days later, Enterprise sailed for the South Pacific to help other U.S. carriers in the Coral Sea.
USS Enterprise (CV-6) 
 The Battle of Midway began on the morning of 4 June 1942, when four Japanese carriers attacked on Midway Island.
USS Enterprise (CV-6) 
 Later in the afternoon, bombers from Enterprise and USS Yorktown sank  (aircraft from Yorktown also sank ).
USS Enterprise (CV-6) 
 When the Naval Battle of Guadalcanal ended on 15 November 1942, Enterprise had helped to sink 16 ships and damage eight more.
USS Enterprise (CV-6) 
 [[File:EnterpriseBurningHellcat.jpg|thumb|This F6F Hellcat crash landed on Enterprise's flight deck.]]
USS Enterprise (CV-6) 
 Enterprise launched planes to strike the Marshall Islands and helped U.S. soldiers land on Kwajalein from 29 January-3 February 1944.
USS Enterprise (CV-6) 
 The end of the "Big E"Enterprise went into the New York Naval Shipyard on 18 January 1946 to be deactivated.
USS Enterprise (CV-6) 
 The citation says:Enterprise also got the Navy Unit Commendation and 20 battle stars for World War II service.
USS Enterprise (CV-6) 
 ReferencesThe Big E: The story of the USS Enterprise, by Edward P Stafford, (1962) comprehensive, well-researched account"Enterprise: America's Fightingest Ship and the Men Who Helped Win World War II,"'' by Barrett Tillman.
Pentagon Force Protection Agency 
 The Pentagon Force Protection Agency (PFPA)  protects and keeps safe the occupants, visitors, and infrastructure of the Pentagon, Navy Annex and other assigned Pentagon facilities.
Pentagon Force Protection Agency 
 PFPA does its job using law enforcement officers (Pentagon Police), criminal investigative and protective services agents; threat management agents; chemical, biological, radiological, nuclear and explosives technicians; and anti-terrorism/force protection and physical security personnel.
Pentagon Force Protection Agency 
 The mission of the Pentagon Police Department (PPD) is to promote high quality law enforcement and security services, in order to provide a safe and orderly work environment for Department of Defense workers in the Washington, DC area.
Pentagon Force Protection Agency 
 Formerly The Defense Protective Service (DPS), The Pentagon Police have exclusive jurisdiction within the Pentagon Reservation and share concurrent jurisdiction with other police agencies in an area of approximately  around the complex.
Pentagon Force Protection Agency 
 Arlington County, Virginia also gave the Pentagon Police officers conditional police authority throughout Arlington County.
Pentagon Force Protection Agency 
 The United States Pentagon Police is also charged with the protection of certain Department of Defense executive officers.