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Unusual diffraction geometries may seem a curiosity but may stimulate novel avenues of application. Not least they illustrate a diversity of diffraction‐measuring possibilities. Laue diffraction including 3‐dimensional detector arrangements is described. The particular congestion of neutron Laue diffraction patterns with big crystals is highlighted. The large‐angle oscillation technique is discussed including the principle with the Ewald sphere construction and practical examples of ‘LOT’ diffraction patterns. Ultra‐fine‐phi‐slicing with perfect or near‐perfect crystals is described. Particular success has been obtained with Laue diffraction where applications to time‐resolved structural intermediates using synchrotron radiation as well as hydrogen and hydration in macromolecular structure are described.

Manfred T. Reetz at the Max-Planck-Institut Mülheim and Philipps-Universität Marburg developed (J. Am. Chem. Soc. 2013, 135, 1665) a mutated Thermoethanolicus brockii alcohol dehydrogenase for the enantioselective reduc­tion of 4-alkylidene cyclohexanone 1. Using a new C₂-symmetic chiral bisphos­phine ligand (Wingphos, 5), Wenjun Tang at the Shanghai Institute of Organic Chemistry reported (Angew. Chem. Int. Ed. 2013, 52, 4235) the rhodium-catalyzed asymmetric hydrogenation of β-aryl enamide 3. Qi-Lin Zhou of Nankai University utilized chiral spirophosphine oxazoline iridium complexes 8a and 8b for the asymmetric hydrogenation of unsaturated piperidine carboxylic acid 6 (Angew. Chem. Int. Ed. 2013, 52, 6072) and 1,1-diarylethylene 9 (Angew. Chem. Int. Ed. 2013, 52, 1556) with excellent selectivities. The iron- catalyzed chemoselective hydrogenation of α,β-unsaturated aldehyde 11 was demonstrated (Angew. Chem. Int. Ed. 2013, 52, 5120) by Matthias Beller at the University of Rostock. Jeffrey S. Johnson at the University of North Carolina at Chapel Hill showed (J. Am. Chem. Soc. 2013, 135, 594) that asymmetric trans­fer hydrogenation of racemic acyl phosphonate 14 yielded β-stereogenic α- hydroxy phosphonate 16, a reversal in diastereoselectivity observed in the case of α-keto ester analogues. Gojko Lalic of the University of Washington developed (Org. Lett. 2013, 15, 1112) a monophasic copper catalyst system for the selective semireduction of terminal alkyne 17. Alois Fürstner and coworkers at Max-Planck-Institut Mülheim reported (Angew. Chem. Int. Ed. 2013, 52, 355) the ruthenium-catalyzed trans- selective hydro­genation of alkyne 19. Macrocyclic alkynes could also be selectively hydrogenated to E- alkenes using this methodology. Bernhard Breit at the University of Freiburg found (Angew. Chem. Int. Ed. 2013, 52, 2231) that a bimetallic Pd/ Re/ graphite catalyst system was highly active for the hydrogenation of tertiary amide 21 to amine 22. Professor Beller also discovered (Chem. Eur. J. 2013, 19, 4437) that a commercially available ruthenium complex allowed for the effective transfer hydrogenation of aromatic nitrile 23 to benzyl amine 24. Notably, no reductive amination side products were observed. Maurice Brookhart at the University of North Carolina at Chapel Hill used (Org. Lett. 2013, 15, 496) tris(pentafluorophenyl)borane as a highly active catalyst for the selective reduction of carboxylic acid 25 to aldehyde 26 with triethylsilane as a hydride source.

Sunggak Kim of KAIST reported (Synlett 2009, 81) an improved protocol for the one-carbon free radical homologation of an iodide such as 1 to the nitrile. Primary, secondary, and tertiary iodides work well. We described (Tetrahedron Lett. 2009, 50, 2462) a procedure for the one-carbon homologation of a halide 4 directly to the benzyl ether 6. Bin Xu of Shanghai University showed (Chem. Commun. 2009, 3246) that conversion of a ketone 8 to the 1,1-dibromoalkene set the stage for the net one-carbon homologation to the amide 9. A. Fernández-Mateos of the Universidad de Salamanca uncovered (J. Org. Chem. 2009, 74, 3913) a powerful new branching reaction, condensing the more substituted center of an epoxide 10 with a nitrile 11 to deliver the adduct 12. Useful diastereocontrol was observed with cyclic epoxides. Uli Kazmaier of the Universität des Saarlandes optimized (Adv. Synthy. Cat. 2009, 351, 1395) a Mo catalyst for the hydrostannation of a terminal alkene 13 to the branched product 14. Dong-Mei Cui of the Zhejiang University of Technology and Chen Zhang of Zhejiang University (both in Hangzhou) developed (Chem. Commun. 2009, 1577) a complementary procedure, converting the terminal alkene 15 into the branched alkenyl tosylate 16. The Wittig reaction is notorious for racemizing sensitive aldehydes. Hélène Lebel of the Université de Montréal demonstrated (Organic Lett. 2009, 11, 41) a simple one-pot protocol for sequential oxidation and homologation of 17 that preserved the integrity of the adjacent stereogenic center. The stereocontrolled construction of trisubstituted alkenes is still a major issue in organic synthesis. Giancarlo Verardo of the University of Udine established (J. Phys. Org. Chem. 2009, 22, 24) that the α-diazo ester 19, readily prepared directly from the simple ester, was converted by I2 to the alkene 20 with high geometric control. Condensation with the Ohira reagent 22 is often the method of choice for converting an aldehyde into the homologated alkyne. Hubert Maehr and Milan Uskokovic of Bioxell and Carl P. Schaffner of the Waksman Institute described (Syn. Commun. 2009, 39, 299) an optimized, scalable procedure for the in situ preparation of 22 and the conversion of 21 to 23. Note, again, that the sensitive stereogenic center adjacent to the intermediate aldehyde was not epimerized under the reaction conditions.

Luigino Troisi of the University of Salento found (Tetrahedron Lett. 2010, 51, 371) that a variety of primary and secondary amines could be coupled with a benzylic halide 1 under carbonylating conditions. Ilhyong Ryu of Osaka Prefecture University showed (Organic Lett. 2010, 12, 1548) that under reducing conditions, an iodide 3 coupled with CO to give the primary alcohol. Felicia A. Etzkorn of Virginia Tech observed (Organic Lett. 2010, 12, 696) that under Hg hydrolysis conditions, the orthothioester derived from 5 coupled with 6 to give 7. Yasuharu Yoshimi of the University of Fukui and Minoru Hatanaka of Iwate Medical University devised (Tetrahedron Lett. 2010, 51, 2332) conditions for the decarboxylative addition of the acid 8 to 9 to give 10. Yong-Min Liang and Xiaojun Yao of Lanzhou University and Chao-Jun Li of McGill University described (J. Org. Chem. 2010, 75, 783) a related procedure with α-amino acids. Yasutaka Ishii of Kansai University established (J. Am. Chem. Soc. 2010, 132, 2536) that t -butyl acetate 12 was an effective partner for the Ir-mediated oxidation-coupling-reduction of an alcohol 11. He used (J. Org. Chem. 2010, 75, 1803) a similar protocol to condense acetone with the diol 14, to give the long-chain diketone 16. The formation of allylic Grignard reagents can be inefficient because the excess reactive halide tends to couple with the Grignard reagent as it forms. Brandon L. Ashfeld of the University of Notre Dame found (Tetrahedron Lett. 2010, 51, 2427) a simple solution to this problem: inclusion of a catalytic amount of the inexpensive Cp2 TiCl2 to mediate the addition of 18 to 17. Brian T. Connell of Texas A&M University demonstrated (J. Am. Chem. Soc. 2010, 132, 7826) that with Mn, 21 could be added to 20. The acetate 21 is thus an easily prepared homoenolate equivalent. Note that although 21 is an E/Z mixture, the product 22 is cleanly Z. Gérard Cahiez of the Université de Paris 13 reported (Synlett 2010, 299) a detailed study of the Cu-catalyzed coupling of 24 with 23. Without supporting ligands, slow addition (syringe pump, 1 h) of 24 to 23 assured clean formation of 25. Manual slow addition (dropping funnel, 15 min) was not effective.

Computational analysis of the Novozyme 435 active site led (Tetrahedron Lett. 2010, 51, 309) Liyan Dai and Hongwei Yu of Zhejiang University, Hangzhou, to t-butanol for the enantioselective monoesterification of 1 to 2. Bruce H. Lipshutz of the University of California, Santa Barbara, devised (J. Am. Chem. Soc. 2010, 132, 7852) a Cu catalyst that mediated the enantioselective 1,2-reduction of α-branched enones such as 3. Qi-Lin Zhou of Nankai University found (J. Am. Chem. Soc. 2010, 132, 1172) that an α-alkoxy unsaturated acid 5 could be hydrogenated with high ee. Tohru Yamada of Keio University desymmetrized (J. Am. Chem. Soc. 2010, 132, 4072) the tertiary alcohol 7, delivering the enol lactone 8. Zachary D. Aron of Indiana University established (Organic Lett. 2010, 12, 1916) that the simple aldehyde 10 effected rapid racemization of the α-amino ester 9. Running the epimerization in the presence of an enantioselective esterase produced 11 high ee. Robert A. Batey of the University of Toronto devised (Organic Lett. 2010, 12, 260) a Pd catalyst for the enantioselective rearrangement of 12 to 13. In the course of a synthesis of dapoxetine, Hyeon-Kyu Lee of the Korea Research Institute of Chemical Technology showed (J. Org. Chem. 2010, 75, 237) that the Rh*-mediated intramolecular C-H insertion of 14 to 15, as developed by Du Bois, gave the opposite absolute configuration to that originally assigned. To prepare α-quaternary amines, Thomas G. Back of the University of Calgary explored (J. Org. Chem. 2010, 75, 1612) the selectivity of the PLE hydrolysis of esters such as 16. Daniel R. Fandrick and colleagues at Boehringer Ingelheim reported (J. Am. Chem. Soc. 2010, 132, 7600) a general method for the catalytic enantioselective propargylation of aldehydes, including 18. Dennis G. Hall of the University of Alberta devised (J. Am. Chem. Soc. 2010, 132, 5544) a route to α-hydroxy esters such as 22 by enantioselective conjugate addition to 21. Alexandre Alexakis of the University of Geneva prepared (Chem. Commun. 2010, 46, 4085) disubstituted epoxides such as 25 by the conjugate addition of 23 to 24.

Takashi Ooi of Nagoya University effected (J. Am. Chem. Soc. 2010, 132, 12240) the enantioselective protonation of ketene silyl acetals such as 1 to give 2 in high ee. Hyeon-Kyu Lee of the Korean Research Institute of Chemical Technology achieved (Org. Lett. 2010, 12, 4184) high ee in the hydrogenation of the cyclic sulfamidate 3 to 4. Doo Ok Jang of Yonsei University combined (J. Am. Chem. Soc. 2010, 132, 12168) the nucleophilic allyl indium with a protonated chiral amine to effect homologation of 5 to 6. Ryo Shintani and Tamio Hayashi of Kyoto University reported (Org. Lett. 2010, 12, 4106) a related advance with tetraarylborates. Kazuaki Ishihara, also of Nagoya University (Org. Lett. 2010, 12, 3502) and Yoshihiro Sohtome and Kazuo Nagasawa of the Tokyo University of Agriculture and Technology (Angew. Chem. Int. Ed. 2010, 49, 9254) devised conditions for adding malonate to imines such as 7. Professors Shintani and Hayashi also employed (J. Am. Chem. Soc. 2010, 132, 13168) tetraarylborates to convert 9 to the α-quaternary amine 10. Professor Ooi (Angew. Chem. Int. Ed. 2010, 49, 5567) and Wanbin Zhang of Shanghai Jiao Tong University (J. Am. Chem. Soc. 2010, 132, 15939) prepared α-quaternary amino acids such as 12 by nucleophilic rearrangement of 11. Keiji Maruoka, also of Kyoto University, reported (J. Am. Chem. Soc. 2010, 132, 17074; not illustrated) a catalytic enantioselective conjugate addition approach to α-quaternary amines. Shuji Akai of the University of Shizuoka converted (Org. Lett. 2010, 12, 4900) the racemic allylic alcohol 13 to the enantiomerically enriched acetate 14 by combining V-catalyzed equilibration with lipase-catalyzed acylation. Toshiro Harada of the Kyoto Institute of Technology added (Org. Lett. 2010, 12, 5270) the alkenylboron 16 to the aldehyde 15 with high ee. Xiang Zhou of Wuhan University and Lin Pu of the University of Virginia significantly improved (Tetrahedron Lett . 2010, 51, 5024) a protocol for the enantioselective addition of aliphatic alkynes to aliphatic aldehydes. For other enantioselective additions to aldehydes (not illustrated), see J. Org. Chem. 2010, 75 , 5326 and Org. Lett. 2010, 12, 5088.

Xiang-Ping Hu and Zhuo Zheng of the Dalian Institute of Chemical Physics developed (Organic Lett. 2009, 11, 3226; J. Org. Chem. 2009, 74, 9191) a family of Rh catalysts for the enantioselective hydrogenation of allylic phosphonates such as 1. Hon Wai Lam of the University of Edinburgh established (J. Am. Chem. Soc. 2009, 131, 10386) that an alkenyl heterocycle 3 could be reduced with high ee. The product 4 could be hydrolyzed to the carboxylic acid. Ken Tanaka of the Tokyo University of Agriculture and Technology showed (J. Am. Chem. Soc. 2009, 131, 12552) that an isopropenyl amide 6 could be hydroacylated with high ee. Gregory C. Fu of MIT observed (J. Am. Chem. Soc. 2009, 131, 14231) that nitromethane 9 could be added to the allenyl amide 8 to give 10, the product of γ-bond formation. Robert K. Boeckman Jr. of the University of Rochester devised (Organic Lett. 2009, 11, 4544) what appears to be a general protocol for the construction of alkylated ternary and quaternary centers: enantioselective hydroxymethylation of an aldehyde 11. In another approach to the construction of alkylated quaternary centers, Varinder K. Aggarwal of the University of Bristol demonstrated (Angew. Chem. Int. Ed. 2009, 48, 6289) that an enantiomerically enriched trifluoroborate salt 14 could be added to an aromatic aldehyde 15 with retention of absolute configuration. The salt 14 was prepared from the corresponding high ee secondary benzyl alcohol. Weinreb amides are versatile precursors to a variety of functional groups. Stephen G. Davies of the University of Oxford devised (Organic Lett. 2009, 11, 3254) a chiral Weinreb amide equivalent 17 that could be alkylated with high de. The minor diastereomer from the alkylation was readily separable by silica gel chromatography. Keiji Maruoka of Kyoto University established (Angew. Chem. Int. Ed. 2009, 48, 5014) that a chiral phase transfer catalyst was effective for the enantioselective alkylation of the alkynyl ester 19. Emmanuel Riguet of the Université de Reims Champagne-Ardenne developed (Tetrahedron Lett. 2009, 50, 4283) an improved catalyst for the enantioselective addition of malonate 22 to cyclohexenone 21.

Yuqing Hou of Southern Illinois University found (J. Org. Chem. 2009, 74, 6362) that the peroxy ether 2 served effectively to directly transfer a methoxy group to the lithiated 1 to give 3. Wanzhi Chen of Zhejiang University, Xixi Campus, showed (J. Org. Chem. 2009, 74, 7203) that pyrimidines such as 4, readily prepared from the corresponding phenol, underwent smooth Pd-catalyzed ortho acetoxylation. Trond Vidar Hansen of the University of Oslo observed (Tetrahedron Lett. 2009, 50, 6339) that simple electrophilic formylation of phenols such as 6 also proceeded with high ortho selectivity. Kyung Woon Jung of the University of Southern California optimized (J. Org. Chem. 2009, 74, 6231) the Rh catalyst for ortho C-H insertion, converting 8 into 9. Jin-Quan Yu of Scripps/La Jolla devised (Science 2010, 327, 315) a protocol for carboxy-directed catalytic ortho palladation that allowed subsequent Heck coupling, transforming 10 into 11. Norikazu Miyoshi of the University of Tokushima established (Chem. Lett. 2009, 38, 996) that in situ generated strontium alkyls added 1,6 to benzoic acid 13, to give, after mild oxidative workup, the 4-alkyl benzoic acid 15. Amin Zarei of Islamic Azad University showed (Tetrahedron Lett. 2009, 50, 4443) that their previously developed protocol for preparing stable diazonium silica sulfates could be extended to the preparation of an aryl azide such as 17. Stephen L. Buchwald of MIT developed (J. Am. Chem. Soc. 2009, 131, 12898) a Pd-mediated protocol for the conversion of aryl chlorides to the corresponding nitro aromatics. Virgil Percec of the University of Pennsylvania has also reported (Organic Lett. 2009, 11, 4974) the conversion of an aryl chloride to the borane, and Guy C. Lloyd-Jones has described (Angew. Chem. Int. Ed. 2009, 48, 7612) the conversion of phenols to the corresponding thiols. Kwang Ho Song of Korea University and Sunwoo Lee of Chonnam National University demonstrated (J. Org. Chem. 2009, 74, 6358) that the Ni-mediated homologation of aryl halides worked with a variety of primary and secondary formamides. Kwangyong Park of Chung-Ang University observed (J. Org. Chem. 2009, 74, 9566) that Ni catalysts also mediated the coupling of Grignard reagents with the tosylate 22 not in the usual way but with the C-S bond to give 23.

(+)-Hirsutellone B 3, isolated from the insect pathogenic fungus Hirsutella nivea BCC 2594, shows good activity (MIC = 0.78 μg/mL) against Mycobacterium tuberculosis. Approaching the synthesis of 3, K. C. Nicolaou of Scripps/La Jolla envisioned and reduced to practice (Angew. Chem. Int. Ed. 2009, 49, 6870) a spectacular tandem intramolecular epoxide opening: internal Diels-Alder cyclization (1 2) that established all three of the carbocyclic rings of 3 with the proper relative and absolute configuration. The construction of 1 began with commercial ( R) -(+)-citronellal 4. Wittig homologation established the ( Z )-iodide 5. Selective ozonolysis followed by condensation with the phosphorane 7 set the stage for Jørgensen-Córdova (Tetrahedron Lett. 2006, 47, 99) epoxidation with H2O2 and a catalytic amount of the Hayashi catalyst 9. Condensation of 10 with the phosphorane 11 followed by Cu-catalyzed coupling of 12 with the organostannane 13 completed the assembly of 1. This approach underscores the strategic advantages of the Jørgensen-Córdova epoxidation over the Sharpless protocol. It is not necessary to reduce the aldehyde to the allyic alcohol, then reoxidize. Furthermore, the Jørgensen-Córdova epoxidation, using catalytic 9, is operationally easier than the Sharpless procedure, which often uses stoichiometric amounts of tartrate ester. The cyclization of 1 proceeded by way of 13, with the newly formed stereogenic center having the diene equatorial on the cyclohexane. Endo cycloaddition catalyzed by the Lewis acid in the solution then gave 2. The facility with which the cyclization of 13 set both the substituents and the stereogenic centers of 2 raises the possibility that the biosynthesis might also follow such an internal [4 + 2] cycloaddition. To complete the synthesis of 3, it was necessary to construct the strained paracyclophane. The authors took advantage of the facile cyclization of the thiolate liberated from 18, then installed the ring-contracted alkene with a Ramburg-Bäcklund rearrangement of 19. They completed the synthesis of (+)-hirsutellone B 3 by exposing the ketone 21 to NH3 in CH3OH/H2O.

The Barton deoxygenation (or Barton–McCombie deoxygenation) is a two-step reaction sequence for the reduction of an alcohol to an alkane. The alcohol is first converted to a methyl xanthate or thioimidazoyl carbamate. Then, the xanthate or thioimidazoyl carbamate is reduced with a tin hydride reagent under radical conditions to afford the alkane. Trialkylsilanes have also been used as the hydride source. Reviews: (a) McCombie, S. W. In Comprehensive Organic Synthesis; Trost, B. M.; Fleming, I., Eds.; Pergamon Press: Oxford, U. K., 1991; Vol. 8, Chapter 4.2: Reduction of Saturated Alcohols and Amines to Alkanes, pp. 818–824. (b) Crich, D.; Quintero, L. Chem. Rev. 1989, 89, 1413–1432. To a solution of the â-hydroxy-N-methyl-O-methylamide (0.272 g, 1.55 mol) in tetrahydrofuran (THF) (30 mL) were added carbon disulfide (6.75 mL, 112 mmol) and iodomethane (6.70 mL, 108 mmol) at 0 °C. The mixture was stirred at this temperature for 0.25 h, and then sodium hydride (60% suspension in mineral, 136.3 mg, 3.4 mmol) was added. After 20 min at 0 °C, the reaction was quenched by slow addition to 60 g of crushed ice. (Caution: hydrogen gas evolution!). The mixture was raised to room temperature and separated, and the aqueous layer was extracted with CH2Cl2 (4 × 15 mL). The combined organic extracts were dried (Na2SO4</aub>), concentrated in vacuo, and purified (SiO2, 5% EtOAc in hexanes) to afford 0.354 g (86%) of the xanthate. To a solution of the xanthate (2.95 g, 11.1 mmol) in toluene (100 mL) was added tributyltin hydride (15.2 mL, 56.6 mmol) and 2, 2´-azobisisobutyronitrile (AIBN, 0.109 g, 0.664 mmol). The reaction mixture was then heated to reflux for 1 h. The mixture was cooled, concentrated in vacuo, and purified (SiO2, 100% hexanes to remove tin byproducts, followed by 10% EtOAc in hexanes to elute product) to afford 1.69 g (96%) of the N-methyl-O-methylamide.

This chapter charts the history of the Peter Pan brand of peanut butter and the hydrogenation process. The 1920s saw progress in the peanut butter industry with the introduction of hydrogenation. Hydrogenation raises the melting point of peanut oil so that it is solid at room temperature, preventing it from separating from the peanut solids. This is why peanut butter with hydrogenated oil doesn't need to be refrigerated. Joseph Rosefield of Alameda, California is widely acknowledged for the first patent to hydrogenate peanut butter. But it was Pittsburgh inventor Frank Stockton who filed a patent for hydrogenating peanut butter on March 17, 1921—almost three weeks before Rosefield. Peter Pan is ordinarily credited as the first hydrogenated peanut butter, but that's not accurate; credit goes to Heinz, whose hydrogenation pedigree dates to 1923.

This chapter charts the history of the Skippy brand of peanut butter. Skippy was launched in 1933, five years after Peter Pan, amid the Great Depression. Skippy peanut butter was the brainchild of Joseph Rosefield (birth name Rosenfield), a native of Louisville, Kentucky. The Rosefield Packing Company would be the most successful business to come out of Alameda, California. Before the company turned its attention exclusively to the manufacture of peanut butter, it was one of the largest pickle makers in the state of California. By the 1920s the Rosefield Packing Company was making its first brand of peanut butter called Luncheon. Rosefield then developed a more successful concept and patented it: stabilizing peanut butter via the process of hydrogenation. Skippy peanut butter expanded rapidly. When Skippy turned profitable in 1940, it began to advertise. Skippy would eventually become America's best-selling peanut butter for more than thirty years.

Carbon dioxide, either as an expanded liquid or as a supercritical fluid, may be a viable replacement for a variety of conventional organic solvents in reaction systems. Numerous studies have shown that many reactions can be conducted in liquid or supercritical CO2 (sc CO2) and, in some cases, rates and selectivities can be achieved that are greater than those possible in normal liquid- or gas-phase reactions (other chapters in this book; Noyori, 1999; Savage et al., 1995). Nonetheless, commercial exploitation of this technology has been limited. One factor that contributes to this reluctance is the extremely complex phase behavior that can be encountered with high-pressure multicomponent systems. Even for simple binary systems, one can observe multiple fluid phases, as shown in Figure 1.1. The figure shows the pressure–temperature (PT) projection of the phase diagram of a binary system, where the vapor pressure curve of the light component (e.g., CO2) is the solid line shown at temperatures below TB. It is terminated by its critical point, which is shown as a solid circle. The sublimation curve, melting curve, and vapor pressure curve of the pure component 2 (say, a reactant that is a solid at ambient conditions) are the solid lines shown at higher temperatures on the right side of the diagram; that is, the triple point of this compound is above TE. The solid might experience a significant melting point depression when exposed to CO2 pressure [the dashed–dotted solid/liquid/vapor (SLV) line, which terminates in an upper critical end point (UCEP)]. For instance, naphthalene melts at 60.1 °C under CO2 pressure (i.e., one might observe a three-phase solid/liquid/vapor system), even though the normal melting point is 80.5 °C (McHugh and Yogan, 1984). To complicate things even further, there will be a region close to the critical point of pure CO2 where one will observe three phases as well, as indicated by the dashed–dotted SLV line that terminates at the lower critical end point (LCEP). The dotted line connecting the critical point of the light component and the LCEP is a vapor/liquid critical point locus.

An increased awareness of global atmospheric carbon levels and heightened efforts to recover industrial emissions prior to their release into the environment has led to the availability of an unprecedented amount of carbon dioxide for industrial utilization. Unfortunately, chemical utilization of carbon dioxide as an industrial feedstock is limited by thermodynamic and kinetic constraints. Toxic carbon monoxide, the main competitor in many processes, is used in industry instead because CO2 is perceived to be less reactive and its efficient catalytic conversion has remained elusive. The major commercial uses of CO2 today are in beverages, fire extinguishers, and refrigerants, where inert physical properties such as oxidative and thermodynamic stability are advantageous. It is this stability that has limited the use of CO2 to only a very few synthetic chemical processes (urea, aspirin, carbonates) despite the enormous availability of this resource. The conversion of CO2 into useful organic compounds will likely rely on the use of metal catalysts to lower energy inputs. Increasingly, the use of supercritical carbon dioxide appears to offer significant advantages in the catalytic activation of CO2 to yield useful products. Liquid or supercritical CO2 (sc CO2) can be used as a reaction medium and can potentially replace conventional organic solvents to serve as an environmentally benign reaction medium (Ikariya and Noyori, 1999; Jessop and Leitner, 1999; Jessop et al., 1995b; Noyori, 1999). A supercritical fluid (SCF) is any substance that has a temperature and pressure higher than their critical values and which has a density close to or higher than its critical density (Jessop and Leitner, 1999; Jessop et al., 1995b). Carbon dioxide has a critical temperature of 31.0 °C and a critical pressure of 71.8 bar. The supercritical region of the phase diagram is the one at temperatures higher than the Tc and pressures higher than the Pc at which the liquid and gas phases become indistinguishable. Below Tc, liquid CO2 can be maintained under relatively modest pressures. Subcritical liquid CO2 behaves like any other nonpolar liquid solvent. Properties such as density are continuous above the Tc and discontinuous below it.

As described in other chapters of this book and elsewhere (Jessop, 1999), a wide range of catalytic reactions can be carried out in supercritical fluids, such as Fischer–Tropsch synthesis, isomerization, hydroformylation, CO2 hydrogenation, synthesis of fine chemicals, hydrogenation of fats and oils, biocatalysis, and polymerization. In this chapter, we describe experiments aimed at addressing the potential of using supercritical carbon dioxide (and carbon dioxide/propane mixtures) for applications in the hydrogenation of vegetable oils and free fatty acids. Supercritical fluids, particularly carbon dioxide, offer a number of potential advantages for chemical processing including (1) continuously tunable density, (2) high solubilities for many solids and liquids, (3) complete miscibility with gases (e.g., hydrogen, oxygen), (4) excellent heat and mass transfer, and (5) the ease of separation of product and solvent. The low viscosity and excellent thermal and mass transport properties of supercritical fluids are particularly attractive for continuous catalytic reactions (Harrod and Moller, 1996; Hutchenson and Foster, 1995; Kiran and Levelt Sengers, 1994; Perrut and Brunner, 1994; Tacke et al., 1998). There are a number of reports on hydrogenation reactions in supercritical fluids using homogenous and heterogeneous catalysts (Baiker, 1999; Harrod and Moller, 1996; Hitzler and Poliakoff, 1997; Hitzler et al., 1998; Jessop et al., 1999; Meehan et al., 2000; van den Hark et al., 1999). We have investigated the selective hydrogenation of vegetable oils and the complete hydrogenation of free fatty acids for oleochemical applications, since there are some disadvantages associated with the current industrial process and the currently used supported nickel catalyst. The hydrogenation of fats and oils is a very old technology (Veldsink et al., 1997). It was invented in 1901, by Normann, in order to increase the melting point and the oxidation stability of fats and oils through selective hydrogenation. Since the melting point increases during the hydrogenation, the reaction is also referred to as hardening. The melting behavior of the hydrogenated product is determined by the reaction conditions (temperature, hydrogen pressure, agitation, hydrogen uptake). Vegetable oils (edible oils) are hydrogenated selectively for application in the food industry; whereas free fatty acids are completely hydrogenated for oleochemical applications (e.g., detergents).