Carbon

5 Key excerpts on "Carbon"

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  eBook - ePub

  BIOS Instant Notes in Chemistry for Biologists

  • J Fisher, J.R.P. Arnold, Julie Fisher, John Arnold(Authors)
  • 2020(Publication Date)
  • Taylor & Francis

    (Publisher)

  All the elements of the periodic table are important for the balance between living and dead things on this planet to be maintained (Section G1). However, Carbon is the most important of all. To illustrate, if all Carbon-containing compounds were removed, the Earth would be as barren as the moon appears. All that would remain is a small residue of minerals and water, as indeed found on the moon.

  Carbon is a component of all foodstuffs, fuels (including wood, gas, and oil), and fabrics (including clothing materials, paper, rubber, etc.).

  At the mid-point of the twentieth century, over 6 million compounds containing Carbon had been identified. This number is growing at the rate of around 1000 new compounds being synthesized or isolated from natural sources each year.

  As a result of Carbon being found in all living things, chemists up until 1828 thought that it was impossible to make organic (living) compounds in the laboratory, rather some ‘vital force ’ must be required. A significant turning point in this branch of chemistry came almost by accident in that year. Friedrich Wohler, on heating a sample of an inorganic salt, ammonium cyanate, produced urea. As urea is a compound found in both blood and urine, it is unquestionably organic (Figure 1 ).

  Figure 1 The synthesis of urea from ammonium cyanate.

  This preparation of an organic compound from inorganic reagents prompted others to attempt to synthesize further organic compounds, and to the rapid expansion in the number of known organic materials.

  Bonding characteristics of Carbon

  There are two major reasons for the huge number of organic compounds. The first relates to the bonding characteristics of Carbon, the second to the isomerism of Carbon-containing compounds, dealt with in Section E1.

  Carbon is a member of Group IV of the periodic table, with a maximum valency of 4 (Sections B1 and A1) and the ability to form regular tetrahedral structures. As the first member of the group, Carbon has an electronegativity (Figure 2 and Section A1) that is in the middle of the electronegativity scale. Therefore, it is generally considered as being neither electropositive nor electronegative, and hence is ideally suited for inclusion in covalent

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  General Chemistry for Engineers

  • Jeffrey Gaffney, Nancy Marley(Authors)
  • 2017(Publication Date)
  • Elsevier

    (Publisher)

  Chapter 1 , organic compounds are those compounds that contain one or more atoms of Carbon covalently bonded to atoms of other nonmetal elements. Due to its ability to also covalently bond to atoms other than Carbon including: nitrogen, oxygen, sulfur, hydrogen, and the halogens, Carbon can make simple as well as extremely complex molecular structures.

  The basic reason for the importance of Carbon relative to the other elements is due to its special bonding and hybridization. Recall that a Carbon atom has an electronic structure of 1s 2 2s 2 2p 2 , so it needs to share four electrons with other atoms in order to obtain the stable electronic configuration of neon (1s 2 2s 2 2p 6 ). Because of this, stable Carbon molecules will always have four bonds per Carbon atom. These bonds can be sigma (σ) bonds or pi (π) bonds, but the number of bonds to Carbon will always add up to four, no more and no less! These four bonds to Carbon always include from two to four hybridized orbitals. Recall from Chapter 3 that the 2s and the 2p valence atomic orbitals of Carbon are close in energy making it possible for them to interact. This interaction results in s -p atomic orbital mixing, called hybridization. Orbital mixing on the Carbon atom can include: the 2s orbital and one 2p orbital (sp hybridization), the 2s orbital and two 2p orbitals (sp 2 hybridization), or the 2s orbital and three 2p orbitals (sp 3

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  Science of Food

  • K. B. Sherrington, P. M. Gaman(Authors)
  • 2010(Publication Date)
  • Routledge

    (Publisher)

  3    Organic Chemistry

  All the components of food, with the exception of water and the mineral salts, are organic compounds. Therefore, a knowledge of organic chemistry is essential in the study of food science and nutrition.

  Organic chemistry is the study of covalent Carbon compounds. All forms of life are based on these organic Carbon compounds. When the term organic chemistry was first introduced, it was thought that these compounds were found only in living organisms and that they could not be produced synthetically. This is now known to be incorrect and a wide variety of organic compounds are produced commercially. Nowadays, it is possible to synthesize vitamins, some sugars and fats, and some simple proteins. Many synthetic organic compounds are an important part of our life; these include plastics, such as polythene and polystyrene, and man-made fibres, such as nylon and polyester.

  Carbon is unique among the elements in that it is capable of forming thousands of different compounds. The reason for this is that Carbon atoms join together very easily and, therefore, a large number of different molecules can be obtained. These molecules are sometimes very large and complex. Carbon atoms, as well as forming bonds with other Carbon atoms, also form bonds with atoms of other elements. The elements which most often combine with Carbon to form organic compounds are hydrogen, oxygen and nitrogen. Sulphur, phosphorus and the halogens (fluorine, chlorine, bromine and iodine) may also be present in organic compounds.

  Carbon has a valency of four, since the four electrons in the outer shell readily form covalent bonds. The covalent bonds can be represented by lines. When a Carbon atom is present in a molecule the atom and bonds can be represented as follows:

  Carbon atoms may be joined by single, double or triple bonds. In a single bond, one pair of electrons is shared between the two Carbon atoms. Two pairs of shared electrons form a double bond and three pairs a triple bond. The conventional representations of single, double and triple bonds are shown in Figure 3.1

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  Carbon Nanotubes

  Properties and Applications

  • Michael J. O'Connell(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  chapter one The element Carbon Frank Hennrich

  Institut für Nanotechnologie

  Candace Chan

  Stanford University

  Valerie Moore

  Rice University

  Marco Rolandi

  Stanford University

  Mike O’Connel

  Theranos, Inc.

  Contents

  1.1	Allotropes of Carbon
  1.2	History
  1.3	Structure
  1.4	Progress of single-walled Carbon nanotube research
  References

  Carbon is the most versatile element in the periodic table, owing to the type, strength, and number of bonds it can form with many different elements. The diversity of bonds and their corresponding geometries enable the existence of structural isomers, geometric isomers, and enantiomers. These are found in large, complex, and diverse structures and allow for an endless variety of organic molecules.

  The properties of Carbon are a direct consequence of the arrangement of electrons around the nucleus of the atom. There are six electrons in a Carbon atom, shared evenly between the 1s, 2s, and 2p orbitals. Since the 2p atomic orbitals can hold up to six electrons, Carbon can make up to four bonds; however, the valence electrons, involved in chemical bonding, occupy both the 2s and 2p orbitals.

  Covalent bonds are formed by promotion of the 2s electrons to one or more 2p orbitals; the resulting hybridized orbitals are the sum of the original orbitals. Depending on how many p orbitals are involved, this can happen in three different ways. In the first type of hybridization, the 2s orbital pairs with one of the 2p orbitals, forming two hybridized sp1 orbitals in a linear geometry, separated by an angle of 180°. The second type of hybridization involves the 2s orbital hybridizing with two 2p orbitals; as a result, three sp2 orbitals are formed. These are on the same plane separated by an angle of 120°. In the third hybridization, one 2s orbital hybridizes with the three 2p orbitals, yielding four sp3 orbitals separated by an angle of 109.5°. Sp3

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  Science in Nursing and Health Care

  • Tony Farine, Mark A. Foss(Authors)
  • 2013(Publication Date)
  • Routledge

    (Publisher)

  organic was originally used to refer to compounds found in organisms, but it then came to mean compounds containing Carbon. Most compounds within the body contain Carbon, and often hydrogen and oxygen too. In current popular usage, the word ‘organic’ has connotations of naturalness and safety, but many of the products of the petrochemical industry, which certainly do not occur in nature, also contain Carbon and are, therefore, organic. In this text, the term ‘organic’ is used in the way a chemist would use it – meaning a substance containing Carbon. In contrast, inorganic chemistry is the study of substances that do not contain Carbon.

    Using the Periodic Table in the appendix, look up the atomic number of Carbon and work out its electron configuration.

  The atomic number of Carbon is 6, and therefore its electron configuration is 2.4.

  Table 3.4 Carbon-atom chain prefixes.

    How many more electrons does Carbon require in order to achieve a stable valence shell?

  The correct answer is 4, and these may of course be obtained by sharing. Were someone to attempt to count the number of organic molecules, the figure would run into millions. One of the reasons for this abundance is the ability of Carbon atoms to bond covalently with each other and thus form chains of varying lengths. Compounds in which the ends of these chains are not joined together are said to be aliphatic , while those in which the chains form a ring are said to be cyclic . Since many of these cyclic compounds have a characteristic smell, they are also known as aromatic . We shall consider examples of each a little later in this chapter. Some of the most important organic molecules within our bodies are carbohydrates , proteins , fats and vitamins . Indeed, they are so important that Chapter 7 has been given over to them along with other substances found in our food. In this section, we concentrate on other important organic molecules, such as alcohols. Let us first clarify how organic molecules are named.

  The names of organic molecules usually begin with a prefix that indicates the length of the Carbon atom chain. Table 3.4 identifies the first ten Carbon atom prefixes. In each case, an example is given from a group of compounds called alkanes

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