Effects of micronized sodium chloride on the sensory profile and consumer acceptance of turkey ham with reduced sodium content

The impact of sodium chloride reduction and its substitution for micronized salt on consumer acceptance of turkey ham was investigated. Five formulations - F1 (control - 2.0% NaCl), F2 (1.7% NaCl), F3 (1.4% NaCl), F4 (1.7% micronized NaCl), and F5 (1.4% micronized NaCl) - were evaluated with respect to sodium chloride content and by consumers using a nine-point hedonic scale for overall acceptability and CATA (check-all-that-apply) using 24 sensory descriptors. Trained panelists characterized the products using the flash profiling technique. Reductions in the salt content by up to 30% did not affect the overall acceptability of the samples by the consumers. However, the consumers characterized the formulations with lower salt content as "less salty and less seasoned" in comparison to the contents in the control. Products containing 1.7% NaCl were considered very similar to the control. The results obtained indicate that it is possible to reduce NaCl content by 30% without affecting consumer acceptance of the product. The use of micronized salt did not affect the sensory characteristics when compared with those of formulations containing the same level of sodium chloride indicating that micronized salt does not influence perception of salt.

Effect of Amaranth addition on the nutritional composition and consumer acceptability of extruded provitamin A-biofortified maize snacks

The objective of this study was to determine the effect of adding Amaranth leaf powder on the nutrient content and consumer acceptability of extruded provitamin A-biofortified (PVA) maize snacks. Flours of four varieties of PVA maize were composited with Amaranth leaf powder at 0, 1 and 3% (w/w) substitution of, respectively, and extruded into snacks. The ash content of the snacks increased from 0.53 g/100 g-0.58 g/100 g to 0.650 g/100g-89 g/100 g and protein content increased from 9.12 g/100 g-10.94 g/100 g when Amaranth was increased from 0% to 3%. Similarly, lysine content increased from 0.10 g/100 g to 0.17 g/100 g, whilst methionine increased from 0.14 g/100 g to 0.19 g/100 g. The provitamin A content of the snacks ranged from 1.29 µg/g to 1.40 µg/g at 0% Amaranth and 1.54 µg/g to 1.78 µg/g at 3% Amaranth. The acceptability of the snacks decreased with increasing Amaranth concentration, only a very small proportion (2-8%) of the panel liked the snacks extremely. PVA maize with added Amaranth leaf powder has a potential for use in nutritious and healthy extruded snacks, but the consumer acceptability of the snacks should be improved.

Industrialization in Sub-Saharan Africa and import substitution policy

This article aims to contribute to the understanding of the process of import substitution in Sub-Saharan Africa. The process of industrialization in Sub-Saharan Africa occurred in two phases: a first step, even very early during the colonial regime began around the 1920s and ended in the late forties; a second phase of industrialization began in the late fifties and gained momentum in the sixties, when import substitution was implemented more widely. Although these countries were the last to embark on the strategy of import substitution, they followed the same steps of Latin American countries, and as the structural domestic and external constraints were too strong, the failure of the policy of import substitution arrived early and the negative impact on these economies had a greater magnitude.

On the effect of molecular structure and composition on the photofragmentation of biomolecules

The research on the interaction between radiation and biomolecules pro-vides valuable information for both radiobiology and molecular physics. While radiobiology is interested in the damage inflicted on the molecule upon irradiation, molecular physics exploits these studies to obtain infor-mation about the physical properties of the molecule and the quantum me-chanical processes involved in the interaction. This thesis work investigated how a small change in the structure or composition of a biomolecule changes the response of the molecule to ioniz-ing radiation. Altogether eight different biomolecules were studied: nucleo-sides uridine, 5-methyluridine and thymidine; amino acids alanine, cysteine and serine; and halogenated acetic acids chloro- and bromoacetic acids. The effect of ionizing radiation on these molecules was studied on molecular level, investigating the samples in gas phase. Synchrotron radiation of VUV or soft x-ray range was used to ionize sample molecules, and the subsequent fragmentation processes were investigated with ion mass spectroscopy and ion-ion-electron coincidence spectroscopy. The comparison between the three nucleosides revealed that adding or removing a single functional group can affect not only the bonds from which the molecule ruptures upon ionization but also the charge localiza-tion in the formed fragments. Studies on amino acids and halogenated acetic acids indicated that one simple substitution in the molecule can dramatical-ly change the extent of fragmentation. This thesis work also demonstrates that in order to steer the radiation-induced fragmentation of the molecules, it is not always necessary to alter the amount of energy deposited on the molecules but selecting a suitable substitution may suffice.

Registered nurses' perceptions of factors impacting on their continuing education /

This qualitative study examined the effects of hospital restructuring on a group of nurses at a community hospital. Eleven nurses were asked questions in order to gain insight into their experience in this situation. Ten of these participants were female, and one was male. The intent was to gather information about how restructuring has affected their lives, including, their motivational factors and barriers to participation in continuing education, and their descriptions of their workplace environment. Audiotaped interviews were conducted on two occasions to obtain this data. Emergent themes included the nurses' comments about continuing education, motivational factors, barriers that included geography and time, reactions of co-workers, restructuring, the College of Nurses' Quality Assurance Program including peer feedback, and performance appraisals. The literature review compares the barriers and motivational factors to the previous research findings. Thus, this study gave voice to the experience of this group of nurses, working in a healthcare setting that is involved in restructuring. This information is important to the healthcare system, since many areas are involved in restructuring. The whole process, if it is to be successful, depends on the frontline workers, namely the nurses. Thus, if there is anything to be learned from this group of people, that could be used to improve this progression, everyone would benefit from this information, were it to be implemented. Everyone is a stakeholder in the quality of healthcare in our province. The frontline workers are the ones that hold the vantage point to be able to provide suggestions for the changes needed to successful. These nurses are not just motivated by work issues however, and educating them and motivating them will also improve the care provided through increased knowledge and enhanced self-esteem.

Construction of bovine adenovirus type 3 E1 and E3, substitution plasmids and the sequencing analysis of DNA pol and pTP /

The relative ease to concentrate and purify adenoviruses, their well characterized mid-sized genome, and the ability to delete non-essential regions from their genome to accommodate foreign gene, made adenoviruses a suitable candidate for the construction of vectors. The use of adenoviral vectors in gene therapy, vaccination, and as a general vector system for expressing foreign genes have been documented for some time. In this study, the objective was to rescue a BAV3 E1 or E3 recombinant vector carrying the kanamycin resistant gene, a dominant selectable marker with useful applications in studying vectored gene expression in mammalian cells. To accomplish the objective of this study, more information about BAV3 DNA sequences was required in order to make the manipulation of the virus genome accessible. Therefore, sequencing of the BAV3 genome from 1 1 .7% to 30.8% was carried out. Analysis of the determined sequences revealed the primary structure of important viral gene products coded by E2 including BAV3 DNA pol and precursor to terminal protein. Comparative analysis of these proteins with their counterparts from human and non human adenoviruses revealed important insights as to the evolutionary lineage of BAV3. In order to insert the kanamycin resistance gene in either E1 or E3, it was necessary to delete BAV3 sequences to accommodate the foreign gene so as not to exceed the limit of the packaging capacity of the virus. To construct a recombinant BAV3 in which a foreign gene was inserted in the deleted E1 region, an E1 shuttle vector was constructed. This involved the deletion from the viral sequences a region between 1.3% to 9% and inserting the kanamycin resistance gene to replace the deletion. The E1 shuttle vector contained the left (0%- 53.9%) segment of the genome and was expected to generate BAV3 recombinants that can be grown and propagated in cells that can complement the missing E1 functions. To construct a similar shuttle vector for E3 deletion, DNA sequences extending from 78.9% to 82.5% (1281 bp) were deleted from within the E3 region that had been cloned into a plasmid vector. The deleted region corresponds to those that have been shown to be non-essential for viral replication in cell culture. The resulting plasmid was used to construct another recombinant plasmid with BAV3 DNA sequences extending from 37.1% to 100% and with a deletion of E3 sequences that were replaced by kanamycin resistance gene. This shuttle plasmid was used in cotransfections with digested viral DNA in an attempt to rescue a recombinant BAV3 carrying the kanamycin resistance gene to replace the deleted E3. In spite of repeated attempts of transfection, El or E3 recombinant BAV3 were not isolated. It seems that other approaches should be applied to make a final conclusion on BAV3 infectivity.

Intramolecular carbenoid insertions : the reactions of [alpha]-diazoketones derived from furanyl, thienyl, benzofuranyl and benzothienyl acetic acids with rhodium (II) acetate /

A number of synthetically useful ring systems can be prepared via the intramolecular insertion of a metal-stabilized carbenoid into a heteroaromatic systems. The chemical outcome of these reactions are dependent not only on the nature of the heteroatom but also on the length of the aliphatic tether linking the carbenoid moiety with the aromatic fragment. Our work with furanyl and thienyl systems containing a single methylene tether have allowed for some rather atypical chemistry. For example, treatment of l-diazo-3-(2-thienyl)-2-propanone (6) with catalytic rhodium (II) acetate yields 5,6- dihydro-4^-cyclopenta[Z>]thiophen-5-one (3) while, the isomeric l-diazo-3-(3-thienyl)-2- propanone(15) gives a spiro-disulphide (20). Novel chemistry was also exhibited in the analogous furanyl systems. While treatment of l-diazo-3-(3-furanyl)-2-propanone (52) with Rh2(OAc)4 resulted in the expected 2-(4-Oxo-2-cyclopentenyliden)acetaldehyde (54), isomeric l-diazo-3-(2- furanyl)-2-propanone (8) undergoes vinylogous Wolff rearrangement to give a mixture of 6a-methyl-2,3,3a,6a-tetrahydrofuro[2,i-^>]furan-2-one (44) and 2-(2-methyl-3-furyl)acetic acid (43). Rhodium acetate catalyzed decomposition of l-diazo-3-(3-benzofuranyl)-2- propanone (84) and l-diazo-3-(2-benzofuranyl)-2-propanone (69)also allows for vinylogous Wolff rearrangement, a chemistry unseen in benzofuranyl systems with longer tethers. A number of interesting products were isolated from the trapping of intermediate ketenes. Decomposition of l-diazo-3-(3-benzothienyl)-2-propanone (100) resulted in the formation of 2,3-dihydro-l//-benzo[^]cyclopenta[^thiophen-2-one (102). However, in addition to (102), a dimer was also generated from the decomposition of l-diazo-3-(2- benzothienyl)-2-propanone (109). The insight into the mechanistic underpinnings of the above reactions are provided by molecular modeling at a PM3 level.

Investigation of single tryptophan proteins encapsulated in TEOS-derived sol-gel matrices by fluorescence spectroscopy /

In the work reported here, optically clear, ultrathin TEOS derived sol-gel slides which were suitable for studies of tryptophan (Trp) fluorescence from entrapped proteins were prepared by the sol-gel technique and characterized. The monitoring of intrinsic protein fluorescence provided information about the structure and environment of the entrapped protein, and about the kinetics of the interaction between the entrapped protein and extemal reagents. Initial studies concentrated on the single Trp protein monellin which was entrapped into the sol-gel matrices. Two types of sol-gel slides, termed "wet aged", in which the gels were aged in buffer and "dry-aged", in which the gels were aged in air , were studied in order to compare the effect of the sol-gel matrix on the structure of the protein at different aging stages. Fluorescence results suggested that the mobility of solvent inside the slides was substantially reduced. The interaction of the entrapped protein with both neutral and charged species was examined and indicated response times on the order of minutes. In the case of the neutral species the kinetics were diffusion limited in solution, but were best described by a sum of first order rate constants when the reactions occurred in the glass matrix. For charged species, interactions between the analytes and the negatively charged glass matrix caused the reaction kinetics to become complex, with the overall reaction rate depending on both the type of aging and the charge on the analyte. The stability and conformational flexibility of the entrapped monellin were also studied. These studies indicated that the encapsulation of monellin into dry-aged monoliths caused the thermal unfolding transition to broaden and shift upward by 14°C, and causedthe long-term stability to improve by 12-fold (compared to solution). Chemical stability studies also showed a broader transition for the unfolding of the protein in dry-aged monoliths, and suggested that the protein was present in a distribution of environments. Results indicated that the entrapped proteins had a smaller range of conformational motions compared to proteins in solution, and that entrapped proteins were not able to unfold completely. The restriction of conformational motion, along with the increased structural order of the internal environment of the gels, likely resulted in the improvements in themial and long-term stability that were observed. A second protein which was also studied in this work is the metal binding protein rat oncomodulin. Initially, the unfolding behavior of this protein in aqueous solution was examined. Several single tryptophan mutants of the metal-binding protein rat oncomodulin (OM) were examined; F102W, Y57W, Y65W and the engineered protein CDOM33 which had all 12 residues of the CD loop replaced with a higher affinity binding loop. Both the thermal and the chemical stability were improved upon binding of metal ions with the order apo < Ca^^ < Tb^"^. During thermal denaturation, the transition midpoints (Tun) of Y65W appeared to be the lowest, followed by Y57W and F102W. The placement of the Trp residue in the F-helix in F102W apparently made the protein slightly more thermostable, although the fluorescence response was readily affected by chemical denaturants, which probably acted through the disruption of hydrogen bonds at the Cterminal end of the F-helix. Under both thermal and chemical denaturation, the engineered protein showed the highest stability. This indicated that increasing the number of metal ligating oxygens in the binding site, either by using a metal ion with a higher coordinatenumber (i.e. Tb^*) which binds more carboxylate ligands, or by providing more ligating groups, as in the CDOM33 replacement, produces notable improvements in protein stability. Y57W and CE)OM33 OM were chosen for further studies when encapsulated into sol-gel derived matrices. The kinetics of interaction of terbium with the entrapped proteins, the ability of the entrapped protein to binding terbium, as well as thermal stability of these two entrapped protein were compared with different levels of Ca^"*^ present in the matrix and in solution. Results suggested that for both of the proteins, the response time and the ability to bind terbium could be adjusted by adding excess calcium to the matrix before gelation. However, the less stable protein Y57W only retained at most 45% of its binding ability in solution while the more stable protein CDOM33 was able to retain 100% binding ability. Themially induced denaturation also suggested that CDOM33 showed similar stability to the protein in solution while Y57W was destabilized. All these results suggested that "hard" proteins (i.e. very stable) can easily survive the sol-gel encapsulation process, but "soft" proteins with lower thermodynamic stability may not be able to withstand the sol-gel process. However, it is possible to control many parameters in order to successfully entrap biological molecules into the sol-gel matrices with maxunum retention of activity.

Towards the enantioselective synthesis of lycoricidine alkaloids /

Two efficient, regio- and stereo controlled synthetic approaches to the synthesis of racemic analogs of pancratistatin have been accomplished and they serve as the model systems for the total synthesis of optically active 7-deoxy-pancratistatin. In the Diels-Alder approach, an efficient [4+2] cycloaddition of 3,4-methylenedioxyco- nitrostyrene with Danishefsky's diene to selectively form an exo-nitro adduct has been developed as the key step in the construction of the C-ring of the target molecule. In the Michael addition approach, the key step was a conjugate addition of an organic zinc-cuprate to the 3,4-methylenedioxy-(B-nitrostyrene, followed by a diastereocontroUed closure to form the cyclohexane C-ring of the target molecule via an intramolecular nitro-aldol cyclization on a neutral alumina surface. A chair-like transition state for such a cyclization has been established and such a chelation controlled transition state can be useful in the prediction of diastereoselectivity in other related 6-exo-trig nitroaldol reactions. Cyclization of the above products fi^om both approaches by using a Bischler-Napieralski type reaction afforded two lycoricidine derivatives 38 and 50 in good yields. The initial results from the above modeling studies as well as the analysis of the synthetic strategy were directed to a chiral pool approach to the total synthesis of optically active 7-deoxy-pancratistatin. Selective monsilylation and iodination of Ltartaric acid provided a chiral precursor for the proposed key Michael transformation. The outlook for the total synthesis of 7-deoxy-pancratistatin by this approach is very promising.A concise synthesis of novel designed, optically pure, Cz-symmetrical disulfonylamide chiral ligands starting from L-tartaric acid has also been achieved. This sequence employs the metallation of indole followed by Sfj2 replacement of a dimesylate as the key step. The activity for this Cz-symmetric chiral disulfonamide ligand in the catalytic enantioselective reaction has been confirmed by nucleophilic addition to benzaldehyde in the disulfonamide-Ti (0-i-Pr)4-diethylzinc system with a 48% yield and a 33% e.e. value. Such a ligand tethered with a suitable metal complex should be also applicable towards the total synthesis of 7-deoxy-pancratistatin.

The kinetics and induced decomposition on the thermal decomposition of hydroperoxides /

This project is focussed on the thermsLl decomposition of t-butyl hydroperoxide and sec-butyl hydroperoxide at 120°C to 160°C in three alcohol solvents. These are methanol, ethajiol and isopropyl alcohol. The aim of the project was to examine the process of induced decomposition. Thermal decomposition of t-hutyl hydroperoxide and sec-butyl hydroperoxide indicate that these reactions have first-order kinetics with activation energies on the order of 20 to 28 K cal/mole, Styrene was used as a free radical trap to inhibit the induced decomposition. The results permitted calculation of how much induced decomposition occurred in its absence. The experimental resvilts indicate that the induced decomposition is important for t-butyl hydroperoxide in alcohol solvents, as shown by both the reaction rate suid product studies. But sec-butyl hydroperoxide results show that the concerted mechanism for the interaction of two sec-butylperoxy radicals occurs in addition to the induced decomposition. Di-sodium E.D,T.A. was added to reduce possible effects of trace transition metal ion .impurities. The result of this experiment were not as expected. The rate of hydroperoxide decomposition was about the same but was zero-order in hydroperoxide concentration.

Synthesis of fluorescent analogues of a-tocopherol as ligands for the human a-tocopherol transfer protein (a-TTP) /

To further understand in vivo localization and trafficking of a-tocopherol (a-Toe), the most biologically active form of vitamin E, between lipid environments, tocopherols are required that can be followed by teclu1iques such as confocal microscopy and fluorescence resonance energy transfer (FRET) assays. To this end, sixteen fluorescent analogues of a-tocopherol (la-d [(1)anthroy loxy -a-tocopherols, A O-a-Toes], 2a-d [w-nitro benzoxadiazole-a-tocopherols, NBD-aToes], 3a-d [w-dansyl-a-tocopherols, DAN-a-Toes], and 4a-d [w-N-methylanthranilamide-atocopherols, NMA-a-TocsD were prepared by substituting fluorescent labels at the terminus of w-functionalized alkyl chains extending from C-2 of the chroman ring while retaining key binding features of the natural ligand. These compounds were prepared starting from (S)-Trolox® acid VIa esterification, protection, and reduction producing the silyl-protected (S)-Trolox aldehyde that was coupled using Wittig chemistry to different w-hydroxyalkylphosphonium bromides. Reduction of the alkene generated the w-hydroxy functionalized 2-n-alkyl intermediates 9a-d having the necessary 2R stereochemistry. A series of functional group manipulations including mesylation, substitution with azide, and hydride reduction provided w-amino functionalized intermediates 12a-d as well. Coupling intermediates 9a-d and 12a-d with the selected fluorophores (9- anthracene carboxylic acid, 4-chloro-7-nitrobenz-2-oxa-l,3-diazole, 5- dimethylaminonapthalene-l-sulfonyl chloride, and I-methyl-2H-3,1-benzoxazine-2,4(1H)dione), followed by deprotection of the phenolic silyl group, gave the desired fluorescent ligands la-d, 2a-d, 3a-d and 4a-d in good yield. Assessment of their binding affinities with recombinant human a-tocopherol transfer protein (ha-TTP) utilizing fluorescent titration binding assays identified competent ligands for further use in protein studies. Compounds Id (C9-AO-a-Toc) and 2d (C9-NBD-a-Toc) both having nonyl alkyl chain extensions between the chromanol and fluorophore were shown to bind specifically to ha-TTP with dissociation constants (KdS) of approximately 280 nM and 55 nM respectively, as compared to 25 nM for the natural ligand 2R,4'R,^'R-a-tocophQxoL.

Synthesis of Chiral Benzimidazolylidenes from 1,10-Phenathrolines and 1,10-Phenathroline-2,9-dione /

A^-heterocyclic carbenes (NHCs) have become the focus of much interest as ancillary ligands for transition metal catalysts in recent years. Their structural variability and strong cy-donation properties have led to the preparation of demonstrably useful organometallic catalysts. Among the three general structural types of NHCs (imidazolylidenes, imidazolinylidenes, and benzimidazolylidenes), benzimidazolylidenes are the least investigated because of the limitation of current synthetic approaches. The preparation of chiral analogues is even more challenging. Previously, our group has demonstrated an alternative approach to synthesizing benzimidazolylidenes with a tetracyclic framework in three steps from 1,10-phenanthroline. This thesis is focused on approaches to chiral benzimidazolylidenes derived from substituted 1,10-phenanthrolines. A key step in the preparation of these ligands involves a reduction of the pyridyl rings in 1,10-phenanthrolines. Chirality can be introduced to phenanthrolines before, during, or after the reduction as illustrated by three approaches: 1) de novo construction of the phenanthroline from chiral ketones with endo and exo faces to provide a degree of diastereoselectivity during subsequent reduction; 2) introduction of substituents into the 2- and 2,9- position of phenanthroline by nucleophilic aromatic substitution, followed by a reduction-resolution sequence; and 3) use of the protected octahydrophenanthroline as a substrate for chiral induction a to nitrogen.

1,1-enediamines and β-substituted enamines in heterocyclic synthesis

The work in this thesis mainly deals with l,l-enediamines and ~ -substituted enamines (push-pull olefines) and their reactions, leading to the formation of a number of heterocycles. Various ~-substituted enamines were prepared by a 'one pot synthesis' in which a l,l-enediamine presumably acts as an intermediate. These enamines, various substituted crotonamides and propenamides, were made by using two different orthoesters, various secondary and primary amines and cyanoacetamide. Their structures, mechanism of formation and geometry are discussed. A synthetic route to various unsymmetrically substituted pyridines was examined. Two substituted pyridinones were obtained by using two different ~-substituted enamines and cyanoacetamide. In one case a dihydropyridine was isolated. This dihydropyridine, on heating in acidic conditions, gave a pyridinone, which confirmed this dihydropyridine as an intermediate in this pyridine synthesis. A new synthetic method was used to make highly substituted pyridinones, which involved the reaction of l,l-enediamines with the ~-substituted enamines. A one pot synthesis and an interrupted one pot synthesis were used to make these pyridinones. Two different orthoesters and three different secondary amines were used. Serendipitous formation of a pyrimidinone was observed when pyrrolidine was used as the secondary amine and triethyl orthopropionate was used as the orthoester. In all cases cyanoacetamide was used as the carbon acid. This pyridine synthesis was designed with aI, l-enediamine as the Michael donor and the ~ -substituted enamines as Michael acceptors. Substituted ureas were obtained in two cases, which was a surprise. Some pyrimidines were made by reacting two substituted enamines with two different amidines. When benzamidine was used, the expected pyrimidines were obtained. But, when 2-benzyl-2-thiopseudourea (which is also an amidine) was used, of the two expected pyrimidines, only one was obtained. In the other case, an additional substitution reaction took place in which the S-benzyl group was lost. An approach to quinazolone and benzothiadiazine synthesis is discussed. Two compounds were made from 1, I-dimorpholinoethene

Intramolecular carbenoid insertion : reactions of [alpha] -diazoketones derived from benzothienyl, pyrolyl and indolyl alkanoic acids with rhodium (II) acetate

Recent studies have shown that the rhodium (II) acetate decomposition chemistry observed for a-diazoketones tethered to thienyl, furanyl, and benzofuranyl moieties is dependent not only on the nature of the heteroatom but also on the length of the aliphatic tether linking the diazoketone moiety with the aromatic fragment. The present thesis expands on these results and focuses on a-diazoketones tethered to benzothiophenes, pyrroles and indoles by a methylene linker. In the case of benzothiophenes, it was shown that the rhodium catalyst decomposition of I-diazo-4-(3-benzothienyl)-2-butanone (146) and 1-diazo-4-(3benzothienyl)- 2-butanone (152) allow for the isolation of 1,2,3a,3b-tetrahydro-3Hbenzo[ b]cyclopenta[1,3]cyclopropa- [1 ,2-d]thiophen-3-one (147) and 1,2,3a,3btetrahydro- 3H-benzo[b]cyclopenta[1,3]cyclopropa[1,2-d]thiophen-3-one (153). However treatment of 1-diazo-3-(3-Benzothienyl)-2-Propanone (165) with Rh(II) acetate results in the formation of 2,3-Dihydro-1H-benzo[b]cyclopenta[d]thiophen-2-one (159), while 1diazo- 3-(2-Benzothienyl)-2-Propanone with the same condition gives 5,5-bis( 1benzothiophen- 2-ylmethyl)-2(5H)-furanone (166) along with the tricycle 159. The chemistry of the pyrrolyl and the indolyl moieties linked to terminal adiazoketone systems was also investigated. The decomposition of I-diazo-(2-pyrrolyl)-2propanone (173) results in the formation of two products; the N-H insertion product IHpyrrolizin- 2(3H)-one (176) and the alkylation product 4,6-dihydrocyclopenta[b]pyrrol5( 1 H)-one (180). When 1-Diazo-3-(3-indoly)-3-propanone (194) is treated with catalytic amount of Rh (II) 3,4-dihydrocyclopenta[b]indol-2(1H)-one (193) is isolated quantitatively. The later reaction when monitored using IH NMR the intermediate 200 can be seen whose structure was confirmed by the comparison to series of model compounds. The mechanisms underlying these reactions as well as their synthetic utility is discussed.

NMR studies of the exchange reactions of CH3CN.BX3 with excess CH3CN /|nJoseph Fogelman. -- 260 St. Catharines, Ont. : [s. n.],

Exchange reactions between molecular complexes and excess acid or base are well known and have been extensively surveyed in the literature(l). Since the exchange mechanism will, in some way involve the breaking of the labile donor-acceptor bond, it follows that a discussion of the factors relating to bonding in molecular complexes will be relevant. In general, a strong Lewis base and a strong Lewis acid form a stable adduct provided that certain stereochemical requirements are met. A strong Lewis base has the following characteristics (1),(2) (i) high electron density at the donor site. (ii) a non-bonded electron pair which has a low ionization potential (iii) electron donating substituents at the donor atom site. (iv) facile approach of the site of the Lewis base to the acceptor site as dictated by the steric hindrance of the substituents. Examples of typical Lewis bases are ethers, nitriles, ketones, alcohols, amines and phosphines. For a strong Lewis acid, the following properties are important:( i) low electron density at the acceptor site. (ii) electron withdrawing substituents. (iii) substituents which do not interfere with the close approach of the Lewis base. (iv) availability of a vacant orbital capable of accepting the lone electron pair of the donor atom. Examples of Lewis acids are the group III and IV halides such (M=B, AI, Ga, In) and MX4 - (M=Si, Ge, Sn, Pb). The relative bond strengths of molecular complexes have been investigated by:- (i) (ii) (iii) (iv) (v] (vi) dipole moment measurements (3). shifts of the carbonyl peaks in the IIIR. (4) ,(5), (6) .. NMR chemical shift data (4),(7),(8),(9). D.V. and visible spectrophotometric shifts (10),(11). equilibrium constant data (12), (13). heats of dissociation and heats of reactions (l~), (16), (17), (18), (19). Many experiments have bben carried out on boron trihalides in order to determine their relative acid strengths. Using pyridine, nitrobenzene, acetonitrile and trimethylamine as reference Lewis bases, it was found that the acid strength varied in order:RBx3 > BC1 3 >BF 3 • For the acetonitrile-boron trihalide and trimethylamine boron trihalide complexes in nitrobenzene, an-NMR study (7) showed that the shift to lower field was. greatest for the BB~3 adduct ~n~ smallest for the BF 3 which is in agreement with the acid strengths. If electronegativities of the substituents were the only important effect, and since c~ Br ,one would expect the electron density at the boron nucleus to vary as BF3on trihalides, the trend is in the opposite direction as determined experimentally. Considerable back-bonding (20), (21) between the halogen and the boron atoms has been proposed as the predominating factor, i.e. ~rt- back-bond between a lone electron pair on the halogen and the vacant orbital on the boron site. The degree of back-bonding varies inversely as the bo~on halogen distance and one would therefore expect the B-F bond to exhibit greater back-bonding character than the B-Cl or B-Br bonds. Since back-bonding transfers electron density from substituent to the boron atom site, this process would be expected to weaken the Lewis acid strength. This explains the Lewis acid strength increasing in the order BF 3 BC1 3 BBr 3 . When the acetonitrile boron trihalide complex is formed, the boron atom undergoes ~_cbange of hybridization from sp2 to sp3. From a linear relationship between the heat of formation of ethyl acetate adducts and the shift in the carbonyl I.R. stretch, Drago (22) et al have proposed that the angular di~tortion of the X-B-X bonds from sp2 (12 ) to sp3 (10 hybridization is proportional to the amount of charge transferred, i.e. to the nature of the base, and they have rejected the earlier concept of reorganization energy in explaining the formation of the adduct bond (19).