Organic Chemistry Reactions

4 Key excerpts on "Organic Chemistry Reactions"

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  eBook - ePub

  Biorenewable Resources

  Engineering New Products from Agriculture

  • Robert C. Brown, Tristan R. Brown(Authors)
  • 2013(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  CHAPTER 3 Organic Chemistry 3.1 Introduction

  Organic chemistry provides the foundation for understanding the transformation of plant materials into biofuels and biobased products. This chapter provides an overview to the subject for readers who are not familiar with the topic or require a brief review. More detailed descriptions can be found in the references at the end of this chapter.

  The original distinction between inorganic and organic compounds was their source in nature. Inorganic compounds were derived from mineral sources, whereas organic compounds were obtained from plants or animals. Advances in chemical synthesis since the eighteenth century have made obsolete these definitions: the vast majority of organic chemicals commercially produced today are made from petroleum. The common feature of organic compounds is a skeleton of carbon atoms that include lesser amounts of other atoms, especially hydrogen, oxygen, and nitrogen, but also sulfur, phosphorus, and halides.

  The high chemical valence of carbon allows for complex structures and large numbers of organic compounds. These include compounds consisting of chains of carbon atoms, referred to as acyclic or aliphatic compounds, and compounds containing rings of carbon atoms, known as carbocyclic or simply cyclic compounds. Some of these rings contain at least one atom that is not carbon (known as heteroatoms). These compounds are called heterocyclic compounds. Carbocyclic compounds are further classified as either aromatic compounds, in which electrons are shared among atoms to produce a particularly stable ring, or alicyclic compounds, which includes all non-aromatic cyclic compounds.

  3.2 Classification of Reactions

  A variety of reactions can occur among organic compounds. Addition reactions occur when two reactants combine to give a single product. Elimination reactions involve the splitting of a single compound into two compounds. Most elimination reactions form a product with a double bond containing the majority of the atoms found in the reactant. Substitution reactions involve replacement of one atom or group of atoms by a second atom or group of atoms. Hydrolysis is a particularly important instance of substitution reactions involving the action of water in splitting a large reactant molecule into two smaller product molecules. One product molecule is bonded to the hydrogen atom from the water, while the other product molecule is bonded to the hydroxyl group derived from the water. Condensation reactions involve two reactants combining to form one larger product with the simultaneous formation of a second, smaller product. Dehydration is a particularly important instance of condensation reactions in which water is the second, smaller product. Note that dehydration is the opposite of hydrolysis. Rearrangement

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  eBook - ePub

  The Chemical Reactions of Life

  From Metabolism to Photosynthesis

  • Britannica Educational Publishing, Kara Rogers(Authors)
  • 2010(Publication Date)
  • Britannica Educational Publishing

    (Publisher)

  CHAPTER 1Biochemical Reactions

  T he study of the chemical substances and processes that occur in plants, animals, and microorganisms has long formed a vital area of science. Biochemical reactions constitute the driving force behind the constant change of organisms, from changes that occur during development to changes that mark the evolution of life. The field of biochemistry deals with the chemistry of life, and as such it draws on the techniques of analytical, organic, and physical chemistry, as well as those of physiologists concerned with the molecular basis of vital processes. All chemical changes within the organism—either the degradation of substances (generally to gain necessary energy) or the buildup of complex molecules necessary for life processes—are collectively described by the term metabolism . These chemical changes depend on the action of organic catalysts known as enzymes, and enzymes, in turn, depend for their existence on the genetic apparatus of the cell. It is not surprising, therefore, that biochemistry enters into the investigation of chemical changes in disease, drug action, and other aspects of medicine, as well as in nutrition, genetics, and agriculture.

  The term biochemistry is synonymous with two somewhat older terms: physiological chemistry and biological chemistry . Those aspects of biochemistry that deal with the chemistry and function of very large molecules (e.g., proteins and nucleic acids) are often grouped under the term molecular biology . The field of biochemistry emerged as an official area of science around 1900. Its origins, however, can be traced back much further. In fact, its early history is part of the early history of both physiology and chemistry.

  HISTORICAL OVERVIEW OF BIOCHEMISTRY

  English scientist Joseph Priestley designed this apparatus for observations on different kinds of gases

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  eBook - ePub

  Reaction Green Metrics

  Problems, Exercises, and Solutions

  • John Andraos(Author)
  • 2018(Publication Date)
  • CRC Press

    (Publisher)

  4   Chemical Reaction Classifications

  4.1 Identifying

  T

  ypes of

  R

  eactions

  There are five major classes of chemical reaction types encountered in organic chemistry: additions, eliminations, rearrangements, redox reactions, and substitutions. Every organic reaction that has ever been discovered or will be discovered in the future can be slotted in at least one of these categories. Generally, most of the named organic reactions that form the workhorse toolbox for organic chemists are categorized uniquely into one of these classes. Modern reactions have attributes that have features of more than one of these classes. Each of these reaction classes may be depicted using a visual algebraic approach using LEGO®-like cartoons to illustrate what is occurring.

  4.1.1 Terms, Definitions, and Examples Additions Addition reactions involve coupling of two or more components in an acyclic (linear) or a cyclic sense. The visual algebraic operation is addition. Eliminations (Fragmentations) Eliminations or fragmentations involve the splitting apart of a substrate or an intermediate. The visual algebraic operation is subtraction. Multi-Component

  Multi-component reactions are a special sub-class of addition reactions involving at least three substrate structures combining together to produce a product. The order of addition of those substrates may or may not matter depending on the reaction mechanism. This is the most powerful method of constructing ring-containing compounds with the least number of reaction steps.

  Rearrangements

  Rearrangement reactions involve a reshuffling of atom connectivity of the substrate or a reaction intermediate. The visual algebraic operation is reshuffling. Rearrangements of substrates always have 100% atom economy. Reactions involving rearrangements of transient intermediates always have atom economies less than 100% since by-products always arise.

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  eBook - ePub

  Pharmaceutical Crystals

  Science and Engineering

  • Tonglei Li, Alessandra Mattei(Authors)
  • 2018(Publication Date)
  • Wiley

    (Publisher)

  The way in which reactions occur in the solid state of organic compounds has long been of interest. On one hand, this interest has arisen from the potential utilization of the limited motion available to the reacting molecules in the solid state toward the synthesis of novel materials [5]. On the other hand, attention has been driven by the aim of probing the reaction mechanisms. Indeed, the range of topics investigated includes the analysis of the influence of the structure on the organic solid‐state reaction process [1], the identification of small changes in molecular packing and their effect on the onset of photoinduced reactions [6], and the control of crystal morphology by the addition of tailor‐made impurities [7]. However, solid‐state reaction mechanisms can be challenging to understand, as similar mechanisms to those applied to the reactions in gas or solutions have sometimes been inadequate. A distinguishing characteristic of solids is their structure, specifically the local structure associated with the reacting species in the crystalline state. Thus, it is not surprising that most studies on organic solid‐state reactions have been focused on X‐ray structural analysis of reactant and product crystals. The rapid progress of single‐crystal X‐ray diffraction and spectroscopic techniques made it possible to understand and explain the dynamic process of a reaction in a crystal. This chapter examines chemical reactivity as it pertains to drug substances mainly in the crystalline state. Pathways and mechanisms of solid‐state reactions, as well as various examples of solid‐state reactions in pharmaceutical applications, are reviewed. A general account, including theories and models of chemical kinetics in solution and solid state, is provided. Factors that affect the rate of chemical reactions are then discussed

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