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    Organic Chemistry I Essentials
    Organic Chemistry I Essentials
    Organic Chemistry I Essentials
    Ebook198 pages1 hour

    Organic Chemistry I Essentials

    By The Editors of REA and Adrian Dingle

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    About this ebook

    REA’s Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Organic Chemistry I includes structure and properties, alkanes, alkenes, alkynes, alkyl halides, stereochemistry, cyclic hydrocarbons, aromatic hydrocarbons, aryl halides, ethers and epoxides, alcohols and glycols, and carboxylic acids.
    LanguageEnglish
    PublisherResearch & Education Association
    Release dateJan 1, 2013
    ISBN9780738670959
    Organic Chemistry I Essentials

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      This book is very precise and to the point, very useful .Thanks for providing such an easy way of learning even the most difficult concepts

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    Organic Chemistry I Essentials - The Editors of REA

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    CHAPTER 1

    STRUCTURE AND PROPERTIES

    1.1 ATOMIC AND MOLECULAR ORBITALS

    Atomic orbitals are arrangements of electrons around the nucleus of an atom. An electron occupies an orbital according to its energy content. In order of increasing energy, the orbitals are specified by the letters , s, p, d, and f, within a given shell. The shells are also arranged in order of increasing energy and are assigned the letters K, L, M, etc.

    In Fig. 1-1, the shapes of some of these orbitals are shown.

    Fig. 1-1 Atomic Orbitals (s and p)

    The overlapping of atomic orbitals leads to the formation of molecular orbitals, and thus molecular bonding (covalent).

    The sigma ( σ) bond, with its characteristic shape, is formed from the overlapping of two s-orbitals, two p-orbitals, or an s and a p-orbital.

    Two molecular orbitals, one bonding and one antibonding, are formed when two atomic orbitals are joined. The bonding orbital is of lower energy and is more stable than the component atomic orbitals. The antibonding orbital is of higher energy and is less stable than the component atomic orbitals. This is shown in Fig. 1-2.

    Fig. 1-2 Formation of two molecular orbitals

    Electrons in antibonding orbitals lead to repulsive forces, which are almost as strong as the attractive forces in bonding orbitals.

    1.2 ELECTRON CONFIGURATION

    The Pauli exclusion principle states that only two electrons can occupy an atomic orbital, and these two must have opposite spins. Electrons with like spins cannot occupy the same orbital.

    Table 1-1 shows the electronic configurations for the first ten elements of the periodic table.

    Following the examples shown in the table, the electronic configuration of Argon is expressed as

    or equivalently

    1s² 2s² 2p⁶ 3s² 3p⁶.

    Table 1-1 Electronic Configurations

    1.3 HYBRID ORBITALS

    The sp hybrid orbitals arise from the mixing of one s orbital and one p orbital. These orbitals are equivalent and much more strongly directed than either the s or p orbital. The sp hybrid orbitals point in exactly opposite directions, which permits them to get as far away from each other as possible.

    The sp² hybrid orbitals arise from the mixing of one s orbital and two p orbitals. These orbitals lie in a plane which includes the atomic nucleus. They are directed to the corners of an equilateral triangle with an angle of 120° between any of two orbitals.

    The sp³ hybrid orbitals arise from the mixing of one s orbital and three p orbitals. These orbitals are directed to the corners of a regular tetrahedron. The angle between any two orbitals is the tetrahedral angle 109.5°.

    1.4 CHEMICAL BONDING

    An ionic bond is the electrostatic attraction between oppositely charged particles, which results from the transfer of electrons.

    An ion-dipole bond is formed if one of the ions in at. ionic bond is replaced by a highly polar molecule, such as water. This bond results from the attraction of the ion to the oppositely charged end of the polar molecule.

    A dipole-dipole bond is formed if the ion in an ion-dipole bond is replaced with another polar molecule. This bond results from the attraction of the oppositely charged ends of the two polar molecules.

    The ionic bonds form stronger bonds than ion-dipole bonds which in turn are stronger than dipole-dipole bonds.

    The formation of covalent bonds by the sharing of electrons results from the overlapping and interaction of partially filled atomic orbitals.

    The degree of the overlapping of the atomic orbitals to form a bonding molecular orbital determines the strength of the covalent bonds.

    Bond length is the distance between bonded nuclei. At this distance the repulsion that occurs between the similarly-charged nuclei balances the packing effect of bonding.

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