2. The fundamentals

Author(s):  
Graham Patrick

‘The fundamentals’ investigates why the element carbon is so suited for the generation of so many compounds. Carbon has atomic number six, meaning it has six protons in its nucleus and six electrons around the nucleus, four of which are valence electrons held in the outer shell. Carbon achieves a stable, full outer shell of electrons by sharing electrons with other elements and other carbon atoms to form covalent bonds. The carbon–carbon bonds are one of the principle reasons why so many organic molecules are possible, including linear chains, branched chains, and rings. The naming of compounds and identification of structures is also explained along with stereochemistry, functional groups, and intermolecular and intramolecular interactions.

2020 ◽  
Author(s):  
Alexis Wolfel ◽  
Cecilia Inés Alvarez Igarzabal ◽  
Marcelo Ricardo Romero

<p>Design of materials with novel sensitivities and smart behaviour is important for the development of smart systems with automated responsiveness. We have recently reported the synthesis of hydrogels, cross-linked by <i>N,N'</i>-diallyltartardiamide (DAT). The covalent DAT-crosslinking points have vicinal diols which can be easily cleaved with periodate, generating valuable a-oxo-aldehyde functional groups, useful for further chemical modification. Based on those findings, we envisioned that a self-healable hydrogel could be obtained by incorporation of primary amino functional groups, from <a>2-aminoethyl methacrylate </a>hydrochloride (AEMA), coexisting with DAT into the same network. The a-oxo-aldehyde groups generated after the reaction with periodate would arise in the immediate environment of amine groups to form imine cross-links. For this purpose, DAT-crosslinked hydrogels were synthesized and carefully characterized. The cleavage of DAT-crosslinks with periodate promoted changes in the mechanical and swelling properties of the materials. As expected, a self-healing behavior was observed, based on the spontaneous formation of imine covalent bonds. In addition, we surprisingly found a combination of fast vicinal diols cleavage and a low speed self-crosslinking reaction by imine formation. Consequently, it was found a time-window in which a periodate-treated polymer was obtained in a transient liquid state, which can be exploited to choose the final shape of the material, before automated gelling. The singular properties attained on these hydrogels could be useful for developing sensors, actuators, among other smart systems.</p>


2006 ◽  
Vol 20 (4) ◽  
pp. 169-176 ◽  
Author(s):  
Jarosław Spychała

In the light of the usefulness of amidines in medicinal chemistry, this paper considers the effects on biological properties and chemical reactivities of organic molecules affected by intramolecular interactions. The study of chemical shifts has been an important source of information on the electronic structure of amidine salts and their ability to form non-covalent bonds with nucleic acids. The NMR and IR results demonstrate that hydrogen bonds are a force for promoting chemical reactions. The thymine O2 carbonyl oxygen in a close proximity to the amidinium cation does interact with the appropriately spaced amidinium NH donor moieties. The1H-15N 2D NMR (GHSQC and GHMBC) spectra with natural isotopic abundance of15N fully confirm the intramolecular character of the bonds. A rule able to estimate the relative strength of the new multifurcated hydrogen bonds is given. The appearance of the ΔδNHchemical shift differences near zero is due to the strong intramolecular interactions. The strength of the H-bond donation by acetamidines is reflected in the N–H dissociation/recombination process (positive charge shift has been invoked to explain other effects on benzamidines). The temperature dependence of chemical shift for the amidine NH protons in dimethyl sulfoxide solutions is herein discussed.


2021 ◽  
Vol 1 (6) ◽  
Author(s):  
Wardatul Istiqomah ◽  
Sri Rahayu ◽  
M. Muchson

The concept of chemistry must be well understood because the concept of chemistry is hierarchical and sequential. In addition, the concept of chemistry is abstract, which can provoke misconceptions. This study aims to identify misconceptions about the covalent bonding material and to determine the percentage of misconceptions about these materials. The results showed that a misconception was observed in 10 concepts of covalent bonding material with the following percentages: 1) 23 percent of the concepts forming elements of covalent compounds, the covalent compounds must be composed of non-metallic elements with non-metallic elements; 2) 69 percent on the Lewis structure concept, the total number of electrons based on the Lewis structure drawing is the number of valence electrons; 3) 54 percent in the concept of double bonds, the breaking energy of the double bonds is twice that of the energy of the single bonds; 4) 35 percent on the concept of covalent coordination bonds, the covalent coordination bonds are shorter than the covalent bonds; 5) 54 percent on the concept of polar covalent bonds and molecular polarity, the pair of binding electrons is located at the same distance between two bonding atoms; 6) 27 percent in the concept of formal charge, the value of the influences of electronegativity in the determination of the formal charge; 7) on the notion of byte rule and the stability of covalent compounds, 27 percent of the stable Lewis structure does not have a free electron pair (PEB) and respects the byte rule; 62 percent chlorine gas will form the Cl2 molecule because it follows the octet rule; and 54 percent of the covalent bonds store chemical energy; 8) 42 percent on the concept of molecular form, the molecular form of a compound is determined by the repulsion of binding electron pairs; 9) on the concept of intermolecular forces and the properties of covalent compounds, 38 percent of the energy required to boil the table salt is superior because the table salt is an ionic bond; and 81 percent of the strongest interactions are hydrogen bonds; and 10) in the concept of valence bond theory, 23 percent of the most important particles in the formation of covalent bonds are valence electrons; and 27 percent electron sharing means sharing one (1) electron with two atoms, as in the case of sharing an apple for two people. Konsep ilmu kimia perlu dipahami dengan baik, karena konsep ilmu kimia berjenjang dan berurutan. Selain itu, konsep ilmu kimia bersifat abstrak, sehingga dapat menyebabkan miskonsepsi. Penelitian ini bertujuan untuk mengidentifikasi miskonsepsi pada materi ikatan kovalen dan mengetahui persentase miskonsepsi pada materi tersebut. Hasil penelitian menunjukkan bahwa miskonsepsi terjadi pada 10 konsep materi ikatan kovalen dengan persentase sebagai berikut: 1) 23 persen pada konsep unsur-unsur pembentuk senyawa kovalen, senyawa kovalen harus tersusun atas unsur non logam dengan unsur non logam; 2) 69 persen pada konsep struktur Lewis, elektron total berdasarkan gambar struktur Lewis adalah jumlah elektron valensi; 3) 54 persen pada konsep ikatan rangkap, energi pemutusan ikatan rangkap dua kali lipat daripada energi pemutusan ikatan tunggal; 4) 35 persen pada konsep ikatan kovalen koordinasi, ikatan kovalen koordinasi lebih pendek daripada ikatan kovalen; 5) 54 persen pada konsep ikatan kovalen polar dan kepolaran molekul, pasangan elektron ikatan terletak pada jarak yang sama diantara dua atom yang berikatan; 6) 27 persen pada konsep muatan formal, nilai elektronegativitas berpengaruh dalam menentukan muatan formal; 7) pada konsep aturan oktet dan kestabilan senyawa kovalen, 27 persen struktur Lewis yang stabil tidak memiliki Pasangan Elektron Bebas (PEB) dan memenuhi aturan oktet; 62 persen gas klorin akan membentuk molekul Cl2 karena memenuhi aturan oktet; dan 54 persen ikatan kovalen menyimpan energi kimia; 8) 42 persen pada konsep bentuk molekul, bentuk molekul suatu senyawa ditentukan tolakan pasangan elektron ikatan; 9) pada konsep gaya antar molekul dan sifat-sifat senyawa kovalen, 38 persen energi yang dibutuhkan untuk mendidihkan garam dapur lebih besar karena garam dapur merupakan ikatan ionik; dan 81 persen interaksi tarik-menarik yang paling kuat adalah ikatan hidrogen; dan 10) pada konsep teori ikatan valensi, 23 persen partikel paling penting dalam pembentukan ikatan kovalen adalah elektron valensi; dan 27 persen sharing electron berarti pemakaian bersama 1 (satu) elektron oleh dua atom, seperti pada kasus berbagi sebuah apel untuk dua orang.


2020 ◽  
Author(s):  
Alexis Wolfel ◽  
Cecilia Inés Alvarez Igarzabal ◽  
Marcelo Ricardo Romero

<p>Design of materials with novel sensitivities and smart behaviour is important for the development of smart systems with automated responsiveness. We have recently reported the synthesis of hydrogels, cross-linked by <i>N,N'</i>-diallyltartardiamide (DAT). The covalent DAT-crosslinking points have vicinal diols which can be easily cleaved with periodate, generating valuable a-oxo-aldehyde functional groups, useful for further chemical modification. Based on those findings, we envisioned that a self-healable hydrogel could be obtained by incorporation of primary amino functional groups, from <a>2-aminoethyl methacrylate </a>hydrochloride (AEMA), coexisting with DAT into the same network. The a-oxo-aldehyde groups generated after the reaction with periodate would arise in the immediate environment of amine groups to form imine cross-links. For this purpose, DAT-crosslinked hydrogels were synthesized and carefully characterized. The cleavage of DAT-crosslinks with periodate promoted changes in the mechanical and swelling properties of the materials. As expected, a self-healing behavior was observed, based on the spontaneous formation of imine covalent bonds. In addition, we surprisingly found a combination of fast vicinal diols cleavage and a low speed self-crosslinking reaction by imine formation. Consequently, it was found a time-window in which a periodate-treated polymer was obtained in a transient liquid state, which can be exploited to choose the final shape of the material, before automated gelling. The singular properties attained on these hydrogels could be useful for developing sensors, actuators, among other smart systems.</p>


Author(s):  
P. F. Hlava

Electron microprobe analysis of materials that contain the lanthanide series of rare earth elements (REE) in natural abundance ratios presents a difficult and truly unique set of problems due to the their chemical and crystallographic similarity and the complexity of the L-spectra used for analysis. REEs differ from one another by the number of protons in their nuclei and the number of electrons in their second inner shell. There are two series of REEs - the lanthanides, from atomic number 58 through 71 and the actinides from 90 through 103. By convention, when most workers speak of the REEs they refer to the lanthanides plus lanthanum, often yttrium and rarely scandium (because these elements are geochemically associated with the lanthanides proper). The terms REE and lanthanide, when used in this paper, will refer to elements of atomic number 57 through 71. In all of these elements the two outer shells, where the valence electrons reside, are essentially identical resulting in chemical behavior that is also essentially identical.


2011 ◽  
Vol 11 (18) ◽  
pp. 9431-9450 ◽  
Author(s):  
S. Compernolle ◽  
K. Ceulemans ◽  
J.-F. Müller

Abstract. We present EVAPORATION (Estimation of VApour Pressure of ORganics, Accounting for Temperature, Intramolecular, and Non-additivity effects), a method to predict (subcooled) liquid pure compound vapour pressure p0 of organic molecules that requires only molecular structure as input. The method is applicable to zero-, mono- and polyfunctional molecules. A simple formula to describe log10p0(T) is employed, that takes into account both a wide temperature dependence and the non-additivity of functional groups. In order to match the recent data on functionalised diacids an empirical modification to the method was introduced. Contributions due to carbon skeleton, functional groups, and intramolecular interaction between groups are included. Molecules typically originating from oxidation of biogenic molecules are within the scope of this method: aldehydes, ketones, alcohols, ethers, esters, nitrates, acids, peroxides, hydroperoxides, peroxy acyl nitrates and peracids. Therefore the method is especially suited to describe compounds forming secondary organic aerosol (SOA).


2011 ◽  
Vol 11 (4) ◽  
pp. 13229-13278
Author(s):  
S. Compernolle ◽  
K. Ceulemans ◽  
J.-F. Müller

Abstract. We present EVAPORATION (Estimation of VApour Pressure of ORganics, Accounting for Temperature, Intramolecular, and Non-additivity effects), a method to predict vapour pressure p0 of organic molecules needing only molecular structure as input. The method is applicable to zero-, mono- and polyfunctional molecules. A simple formula to describe log10p0(T) is employed, that takes into account both a wide temperature dependence and the non-additivity of functional groups. In order to match the recent data on functionalised diacids an empirical modification to the method was introduced. Contributions due to carbon skeleton, functional groups, and intramolecular interaction between groups are included. Molecules typically originating from oxidation of biogenic molecules are within the scope of this method: carbonyls, alcohols, ethers, esters, nitrates, acids, peroxides, hydroperoxides, peroxy acyl nitrates and peracids. Therefore the method is especially suited to describe compounds forming secondary organic aerosol (SOA).


2014 ◽  
Vol 11 (2) ◽  
pp. 527-530
Author(s):  
Baghdad Science Journal

In this research the Inter-Particle Expectation Values have been studied for atomics Helium (He) and Beryllium (Be) also for He-like ions, Be-like ions (Li-1, B+1? Li+1, Be+2, B+3) by using Hartree-Fock wave functions, We compared the results to some ions which have the same atomic number from each group with atomic number, We compared the results with published calculations to the last studied .


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