The Synthetic Methods Structures, and Properties of the Ca-C σ Bond Organocalcium Containing Compounds E-Book
Nejib Ben Hussein Mekni
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- Herausgeber: Bentham Science Publishers
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
This reference describes the chemistry of organocalcium compounds that contain a Ca-C σ-bond. It collects the information about this niche group of organometallic compounds into 4 easy-to-read chapters. It is intended for scholars in the field of organic chemistry, and researchers in industrial chemistry and chemical engineering departments.
Key features:
- Presents a comparison to homologous compounds of other alkaline earth metals.
- Explains the main problems encountered in the synthesis of organocalcium compounds with reference to the reactivity of calcium, the low solubility in common solvents and the high reactivity of the formed intermediates and products
- Highlights many concepts about the Ca-C bond such as the steric hindrance, degrading agent properties, organocalcium spectroscopy, and more
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Seitenzahl: 134
Veröffentlichungsjahr: 2002
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PREFACE
The organocalcium compounds may include organic compounds that contain calcium atom(s) in their molecular formula, in which calcium is not bonded to carbon atoms, but generally bonded to a heteroatom (e. g. O, N, S, etc.) as an ionic bond or coordinated to heteroatoms as complexes.
As a contribution to the organometallic field and especially the organocalcium chemistry, the organocalcium compounds that contain Ca-C σ-bond are described here. The main problems encountered in the synthesis of such compounds compared to their homologous organomagnesium derivatives are expected to be due to the low reactivity of calcium element, the low solubility in common solvents and the high reactivity of the formed intermediates and products and their instability, are detailed and discussed.
We scanned the different Ca-C σ-bond containing organocalcium compounds and compared some of their properties to those of the alkaline and alkaline earth organometallic homologous compounds.
In this work, several important notes such as the restriction of the Ca-C double bond from real experimental examples are highlighted. Calcium may form two σ-bonds with two different carbon atoms in very difficult geometrical situations in the presence of high hindrances under the effect of bulky groups, but it cannot form a double bond. Besides, many interesting ideas such as degrading agent property, organocalcium spectroscopy and others are discussed.
In addition to research groups in the academic field of organometallic compounds, many other readers may benefit from this book reference as well as the catalyst, polymer, petroleum, pharmacology and pipeline fields, especially in the scarcity of reference books on the subject.
CONSENT FOR PUBLICATION
Not applicable.
CONFLICT OF INTEREST
The author declares no conflict of interest, financial or otherwise.
ACKNOWLEDGEMENTS
Declared none.
ACKNOWLEDGEMENTS
The authors would like to thank their colleague Dr. Amr Eddeck, a member of Taibah University teaching and research staff (Saudi Arabia), Miss Nour El Houda Mekni and the professor Sliman Ben Ghorbal for their helpful technical efforts and Pr. Dr. Mohamed Abderrahmane Sanhoury, Ph.D., MRSC (Member of the Chemical Royal Society) for technical and language assistance.
We thank all our professors from the Faculty of Sciences of Tunis (Tunisia), all our colleagues, and all our teachers.
We dedicate this work to the Soul of our fathers, our mothers, our wives and all our family members.
General Introduction
Nejib Ben Hussein Mekni,Nourdine RaouafiAbstract
This first chapter is a general introduction to the book in which we give a background on the Ca-Cσ-bond containing organocalcium compounds, which are less studied as compared to other organometallic compounds.
We describe the interest in synthesizing the synthesized organometallic intermediates and products as well as their application fields such as chemistry, biology, medicine, pharmacology, and industry.
It is indicated that such compounds are not well-known because of the low reactivity of calcium elements, the low solubility of oraganocalcium intermediates and products in common organic solvents, their instability resulting from their high reactivity, cause their degradation and the degradation of their preferred ethereal solvents.
Despite the significant difference in electronegativity value between the two elements, the Ca-Cσ-bonds have a covalent polar character. In many cases, the coordination considerably decreases the calcium electropositive character, facilitating the formation of the Ca-Cσ-covalent bond.
The difficulties in synthesizing such compounds, their degradation property and catalytic behaviour as well as the spectroscopy technics used to identify their structures are also described.
General Introduction
Organometallic compounds are increasingly attracting great interest as witnessed by the number of their newly synthesized intermediates and products, involving different applications, in chemistry, biology, medicine, pharmacology, and industry fields.
Compared to the other alkali, alkaline earth and transition element organometallic derivatives, the Ca-Cσ-bond containing organocalcium compounds are less known for many reasons, which are related to the low reactivity of calcium element, the low solubility of the oraganocalcium intermediates and products in common organic solvents, their instability coming from their high reactivity, that causes their degradation and the degradation of their preferred ethereal solvents.
The high difference in electronegativity value between calcium and carbon elements could be expected to result in the formation of a Ca-C ionic bond. However, the observed Ca-Cσ-bond confirms its polar covalent character. The formation of such bonds may be due to the high coordination number of calcium atom from its d-vacuum orbitals to both n lone electron pairs of heteroatoms of the main product as well as the ethereal solvents and to the π-bonding pairs. Such coordination would considerably decrease the calcium electropositive character, yielding the formation of a Ca-Cσ-covalent bond.
From the above-described behavior, we were inspired in this work by the idea of grouping all information and the behavior of such compounds. So, our main goal is focused on the organocalcium compounds that contain Ca-Cσ-bond.
Herein, we enumerate the synthetic methods and encountered difficulties, the structures, degradation and catalytic behaviour of such compounds and the spectroscopic techniques used to identify their structures.
We have grouped almost all kinds of previously synthesized Ca-Cσ-bond containing organocalcium intermediates and products including alkylcalcium, allylcalcium, alkynylcalcium, diene calcium, diyne calcium phenylcalcium, benzylcalcium, arene calcium and heteronuclear aromatic calcium derivatives.
Conclusion
The polar covalent Ca-Cσ-bond-containing compounds are less known than the other organometallic compounds; because of the different encountered problems, before, and during the synthetic process.
The n and π electron pairs of organic compounds coordinate to the d-vacuum orbitals of calcium atom, to decrease its electrophilicity and facilitate the formation of the Ca-C bond.
This work grouped all kinds of synthesized Ca-Cσ-bond containing compounds, the encountered synthetic problems, and their solutions.
Calcium Element
Nejib Ben Hussein Mekni,Nourdine RaouafiAbstract
In this second chapter, we have grouped the physical and chemical properties of elemental calcium and calcium cation species as well as their importance in the human body, especially in the skeleton and cell, as well as their applications in the chemical, electrical, and biological life fields.
In a nutshell, we describe the history of the organocalcium Ca-Cσ-bond containing compounds.
Then, we expose the encountered challenges and difficulties in the synthesis of organocalcium Ca-C containing compounds: before, during and after the organocalcium preparation and the solutions to overcome these difficulties.
We have grouped the calcium activation methods, the nature of the solvent, the substrate structure, temperature and the optimal experimental reaction conditions.
1. Calcium element
1.1. Introduction
Calcium is the fifth most abundant element by mass in both Earth's crust and seawater (3.4%) [1-3] and the most abundant mineral in the human body. Likewise, calcium cation (Ca2+) is the fifth-most-inexhaustible dissolved seawater metallic ion by both mass and molarity [4, 5]. Calcium element was isolated for the first time by Humphry Davy in 1808 [6, 7]. It is the second alkaline earth metal in the periodic table, with two allotropes [8].
External to earth, two ionized calcium lines were detected (H- and K- lines at 3968.5 Å and 3933.7 Å, respectively) in the visible spectra of many stars, including the sun [9].
Calcium weighs more than 1 Kg in the adult human body. It is essential for living organisms, especially as a cellular ionic messenger, with many other functions, such as the stabilization of the endoskeleton. Particularly, the passage of the calcium through the cytoplasm represents the signal for many cellular processes, including cellular mobility, neuronal transmission as in excitatory synapse [10], fertilization [11], cell growth [12] or proliferation [12, 13], muscle contraction [14], learning [14, 15], memory [16, 17], and saliva secretion [18, 19]. The study of calcium flagging can be monitored by loading the cell’s cytoplasm with a calcium-sensitive fluorescent dye for example Fura-2 [20, 21].
In its solid state (elemental metallic form), calcium is hazardous, causing violent reactions with water and acid contact (producing hydrogen [22]). Because of its high reactivity with oxygen and sulfur-containing impurities, calcium is also used in metallurgy as decarbonizer, deoxidizer, and desulfurizer to produce some alloys [23]. When lit, calcium burns in the air producing a high-intensity orange-red brilliant light.
Calcium ion and most calcium compounds, found in many foods and useful materials have low toxicity. But, a high calcium intake or absorption contributes to the development of kidney stones [24-26] and causes few serious health problems. When swallowed, calcium metal can be fatal [27]. In addition, some studies have suggested that excessive intake of calcium as supplements could cause an increased cardiovascular mortality [28-31]; however, other investigations found that there is no risk [32].
1.2. Calcium Physical Properties
Calcium is a silvery metallic element, extracted through electrolysis from calcium-containing compounds such as calcium chloride. It is harder than lead, with a lower electrical conductibility than aluminium and copper. It has potential uses as wiring in off-world applications [33] but its use in other application fields is limited by its high reactivity with air.
Among the known 26 isotopes of calcium (35Ca to 60Ca), there are five stable isotopes (40Ca, 42Ca, 43Ca, 44Ca, 46Ca), one that has a long half-life (47Ca) and a cosmogenic isotope (48Ca), and one radioactive 41
