Functional Groups

9 Key excerpts on "Functional Groups"

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  eBook - ePub

  Chemistry

  With Inorganic Qualitative Analysis

  • Therald Moeller(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  32

  ORGANIC CHEMISTRY: Functional Groups AND THE MOLECULES OF BIOCHEMISTRY

  Publisher Summary

  This chapter discusses the most common Functional Groups of the two main types, such as groups with only covalent single bonds and groups that include covalent double bonds. It explains the nomenclature of compounds containing those groups. The chapter describes proteins, carbohydrates, lipids, and nucleic acids, which are the molecules of biochemistry. A functional group is an atom or group that bonds to one or more carbon atoms in an organic molecule and contributes a characteristic chemical behavior to the molecule. In organic compounds, the OH group is usually covalently bonded and is called the hydroxyl group. The attachment of a hydroxyl group to an aromatic ring gives a class of organic compounds known as phenols, ArOH. Replacement of the hydrogen atoms of an ammonia molecule by hydrocarbon groups gives amines. The carbonyl group consists of a carbon atom and an oxygen atom joined by a covalent double bond. An aldehyde, RCHO, is a compound in which a hydrogen atom and a hydrocarbon group are bonded to a carbonyl group. Ketones are used extensively as solvents, especially in lacquers. A carboxylic acid, RCOOH, has a functional group that is a combination of a carbonyl group and a hydroxyl group. The chapter explains the concept of infrared and ultraviolet spectroscopy.

  In this chapter the most common Functional Groups of the two main types—groups with only covalent single bonds and groups that include covalent double bonds—are discussed. The nomenclature of compounds containing these groups is explained. Examples are given of some simple compounds and some more complex compounds of specific interest containing each of the groups. A few of the most common preparations and reactions of the various types of compounds are included. The chapter (and the book) ends with a brief introduction to proteins, carbohydrates, lipids, and nucleic acids—the molecules of biochemistry.

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  Chemical Methods in Gas Chromatography

  • V.G. Berezkin(Author)
  • 2000(Publication Date)
  • Elsevier Science

    (Publisher)

  Chapter 9 Functional group analysis 9.1. INTRODUCTION One of the most important problems in analytical chemistry is the identification and determination of a substance in a pure form or in a mixture. To solve this problem, wide use is made of methods of functional group analysis, the object of which is the qualitative and quantitative determination of various Functional Groups in a sample or in its fractions. In the functional group analysis of organic compounds it is assumed that an organic molecule can be considered as a sum of virtually independent Functional Groups whose properties determine the physical and chemical properties of the compound. In iden- tifying complex molecules, however, we must take account of the mutual effect of func- tional groups which can cause an ‘unexpected’ change in the properties of these groups and a deviation in the properties observed from those expected theoretically in accor- dance with a simple additive scheme. In functional group analysis, wide use is made of chemical methods as they are univer- sal and selective.

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  The Chemistry of Beer

  The Science in the Suds

  • Roger Barth(Author)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  It is convenient to think about the molecules on the basis of collections of atoms that form parts of the molecules. These collections are called groups or Functional Groups. Families of compounds are classified by the Functional Groups they contain. For example a molecule with an −OH group attached to a carbon atom that has no other oxygen attached is an alcohol. Each group imparts particular behavior to the molecule or to part of the molecule. This approach is useful, but not perfectly exact. Molecules with the same func- tional groups may still differ in many ways, and sometimes molecules display unexpected behavior not predicted on the basis of the Functional Groups. Many biological molecules have multiple Functional Groups and belong to several families at the same time. 108 INTRODUCTION TO ORGANIC CHEMISTRY Alkanes and Alkyl Groups An alkane is a compound containing only carbon and hydrogen atoms and only single bonds. A portion of a molecule that has only carbon and hydrogen and only single bonds is called an alkyl group. Chemists tend to think of alkanes as the absence of functionality. Because C−H and C−C bonds have low to no polarity, alkanes are essentially nonpolar. Regions of a molecule that have only alkyl groups are hydrophobic, that is, they avoid polar molecules like water and they interact best with nonpolar molecules or with nonpolar regions of molecules. Some examples of alkyl groups are shown in different representations in Figure 5.3. Each alkyl group is shown with an extra bond (in red) that serves as the point of attachment to the rest of the molecule. The difference between the 1-propyl (also called n-propyl) group and the 2-propyl (also called isopropyl) group is the point of attachment. The 1-propyl group attaches to the rest of the molecule by its end carbon and the 2-propyl group attaches by its middle carbon. The C−C single bonds in alkyl groups can rotate freely, so the shapes of molecules with alkyl groups are not usually fixed.

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  eBook - ePub

  Organic Chemistry Concepts

  An EFL Approach

  • Gregory Roos, Cathryn Roos(Authors)
  • 2014(Publication Date)
  • Academic Press

    (Publisher)

  Chapter 7

  Functional Classes II, Reactions

  Abstract

  This chapter focuses on the reactions of Functional Groups. The concepts of structure, reactivity, and acids/bases from Chapters 1–6 are applied. The major reactions of Functional Groups are discussed through numerous examples. Certain reactions are highlighted as visual tools to identify Functional Groups. Some simple mechanisms are detailed in order to show important features.

  Keywords

  Acetal; Acylation; Alkylation; Combustion; Condensation; Dehydration; Diagnostic test; Electrophilic addition; Electrophilic aromatic substitution; Elimination; Epoxidation; Free radical substitution; Grignard; Haloform; Halogenation; Hydrate; Hydration; Hydrogenation; Hydroxylation; Markovnikov; Metal hydride; Nucleophilic acyl substitution; Nucleophilic substitution; Organometallic; Oxidation; Ozonolysis

  7.1. Functional Group Interconversions

  Chapters 1 –3 introduced the main structural features of the important classes of organic molecules and their Functional Groups. Chapters 4 –6 explained the concepts which affect reactivity and help you to understand the organic reactions of simple functional group conversions.

  The purpose of this chapter is to apply the concepts from Chapters 1 –6 by using many different reactions as examples. The equations and schemes in this chapter show how the ideas from the earlier chapters allow to you understand and predict the reactions for the different Functional Groups.

  This book does not show these reactions leading to very complex molecules. Instead, a small number of examples are used to show the type of reaction which is expected with each of the Functional Groups.

  Unlike most books, we do not separate the processes of Functional Group Preparations and Functional Group Reactions. These are really one and the same, because the preparation of one functional group is simply the reaction of another. If a reaction product has a different functional group from the starting reagent, it means the reaction is a method for making this functional class. This approach gives you a clearer picture of functional group relationships.

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  Chemistry, 5th Edition

  • Allan Blackman, Steven E. Bottle, Siegbert Schmid, Mauro Mocerino, Uta Wille(Authors)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  O O H H We can therefore predict that both molecules will undergo a reaction called oxidation, in which the CHO group is converted to a COOH (carboxylic acid) functional group. Similarly, both compounds will react with species called reducing agents, which will convert the CHO group to a CH 2 OH (primary alcohol) group. We will learn a lot more about the specific reactions involved later in this text. It therefore makes sense to name organic compounds according to their Functional Groups, and we will learn how this is done in this part of the chapter. But first, the common Functional Groups that you will encounter are outlined in table 2.7. Note that R is a commonly used symbol to denote either a hydrogen atom or an alkyl group (see table 2.9). You should be able to identify the presence of each of these Functional Groups in any molecule. TABLE 2.7 Common Functional Groups Functional group Name of group Found in R = R O H hydroxyl alcohols C C O R H carbonyl aldehydes C or H C O R R carbonyl ketones C C O R OH carboxyl carboxylic acids C or H Alcohols The OH (hydroxyl) group is present in all alcohols. It is attached to a carbon atom, which itself may be attached to one, two or three other carbon atoms (the exception is methanol, CH 3 OH, which contains only CHAPTER 2 The language of chemistry 63 one carbon atom). Alcohols are classified as primary (1°), secondary (2°) or tertiary (2°) according to this number, as shown in figure 2.25. We can also classify carbon atoms within molecules according to this scheme. Thus a carbon atom attached to one carbon atom (as in a primary alcohol) is called a primary carbon atom, a carbon atom attached to two carbon atoms (as in a secondary alcohol) is called a secondary carbon atom and a carbon atom attached to three carbon atoms (as in a tertiary alcohol) is called a tertiary carbon atom (figure 2.25).

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  Spot Tests in Organic Analysis

  • F. Feigl, V. Anger(Authors)
  • 2012(Publication Date)
  • Elsevier Science

    (Publisher)

  In contrast to ions, Functional Groups are not independent participants; instead they represent only the active portions of the molecular species participating in the reaction. Consequently, the remainder of the molecule has an influence on the solubility of the particular compound and its reaction products in either water or organic liquids, on the speed and extent of the reactions, and also on the color of the reaction products in daylight or ultraviolet light. In isolated cases the influence of the remainder of the organic molecule on the reactivity of Functional Groups may be so extensive that certain com-pounds do not respond at all to tests for these groups, even though expe-rience with other compounds containing these groups has shown the tests to be effective. As a rule, these deviations from the general pattern are only a matter of degree. Accordingly, the limits of identification vary widely at times when compounds containing the same functional group are tested imder like conditions. A study of the table following Chap. 7 is enlightening in this respect. Tests for Functional Groups do not necessarily demand that the test material be in solution. Sometimes fusion or sintering reactions can be made with the solid sample. In such cases, because of the higher temperature and absence of dilution, reactions may sometimes be realized which do not occur at all in solution. Spot test analysis also makes use of the reactions of gaseous thermal fission products, which are brought into contact with suitable reagents, and thus reveal the presence or absence of particular Functional Groups. Reactions in the vapor phase deserve special attention when testing for Functional Groups in compounds which are volatile at room temperature or on gentle warming. If this is the case, a test which is merely selective when conducted in solution, can be rendered specific for an individual vola-tile or sublimable compound.

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  Organic Chemistry

  • T. W. Graham Solomons, Craig B. Fryhle, Scott A. Snyder(Authors)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  You should learn to identify these common Functional Groups as they appear in other, more complicated molecules. 76 CHAPTER 2 Families of Carbon Compounds 2.12A Functional Groups in Biologically Important Compounds Many of the Functional Groups we have listed in Table 2.3 are central to the compounds of living organisms. A typical sugar, for example, is glucose. Glucose contains several alcohol hydroxyl groups ( OH) and in one of its forms contains an aldehyde group. Fats and oils contain ester groups, and proteins contain amide groups. See if you can identify alcohol, alde- hyde, ester, and amide groups in the following examples. Glucose OH O OH OH HO HO A typical fat O n n n O O O O O *Two useful handbooks are Handbook of Chemistry, Lange, N. A., Ed., McGraw-Hill: New York; and CRC Handbook of Chemistry and Physics, CRC: Boca Raton, FL. HELPFUL HINT Understanding how molecular structure influences physical properties is very useful in practical organic chemistry. 2.13 Physical Properties and Molecular Structure So far, we have said little about one of the most obvious characteristics of organic compounds— that is, their physical state or phase. Whether a particular substance is a solid, a liquid, or a gas would certainly be one of the first observations that we would note in any experimental work. The temperatures at which transitions occur between phases—that is, melting points (mp) and boiling points (bp)—are also among the more easily measured physical proper- ties. Melting points and boiling points are also useful in identifying and isolating organic compounds. Suppose, for example, we have just carried out the synthesis of an organic compound that is known to be a liquid at room temperature and 1 atm pressure. If we know the boiling point of our desired product and the boiling points of by-products and solvents that may be present in the reaction mixture, we can decide whether or not simple distillation will be a feasible method for isolating our product.

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  Understanding Advanced Organic and Analytical Chemistry

  The Learner's ApproachRevised Edition

  • Kim Seng Chan, Jeanne Tan;;;(Authors)
  • 2016(Publication Date)
  • WS EDUCATION

    (Publisher)

  CHAPTER 1

  Structure and Bonding

  1.1 Introduction

  Hearing the words “organic chemistry” may strike fear in some students, but this should not be the case at all. You may have come across complex-looking structures, alien-looking mechanisms and reactions. Exam questions about such may confuse you and heighten anxiety, but the answers to these questions need not be highly sophisticated, as these usually stem from the basic principles of organic chemistry that are covered in this book.

  Organic chemistry is mainly the study of carbon-containing compounds, excluding those classified as inorganic compounds, such as carbonates and oxides.

  It is commendable that the carbon element is able to form chains upon chains, resulting in millions of uniquely different compounds. This remarkable feat cannot be reproduced even by its closest group member, silicon, in the periodic table.

  Although there are numerous organic compounds in existence, one can easily identify various specific combinations and arrangements of atoms that are responsible for the chemical behavior of these compounds. These atoms or group of atoms are known as Functional Groups, and we will set out to discuss their characteristic properties in this book.

  In subsequent chapters, we will look into the properties of simple organic compounds grouped into homologous series according to the functional group present. Some of these are presented in Table 1.1 . Before we get into the organic chemistry proper, we need to be able to interpret what structures such as those in Table 1.1 represent. The naming of simple organic compounds will be covered under each chapter on the homologous series.

  Table 1.1 Common Functional Groups and Homologous Series.

  1.2 Constitutional/Structural Formulae of Organic Compounds

  The molecular formula of a compound informs us of the number and type of atoms present in a molecule. But it may not give us information on how the various atoms are actually connected to one another. For instance, the molecular formula C4 H8 O2

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  Organic Synthesis Via Examination Of Selected Natural Products

  • David J Hart(Author)
  • 2011(Publication Date)
  • World Scientific

    (Publisher)

  The second topic can be a helpful consideration when developing synthetic strategies, and is reveal-ing when analyzing published syntheses. For example, we will see how such an analysis shows why cyclohexenes and cyclopentenes can serve as precursors of 5- and 6-membered rings, respectively (recall the Johnson approach to progesterone). We will start with some general considerations and then move to examples from syntheses we have already seen. Functional Group Reactivity Patterns and Difunctional Relationships 205 206 Organic Synthesis via Examination of Selected Natural Products Useful Books Ireland, R. E. Organic Synthesis, Prentice-Hall, 1969 (147 pages) Fleming, I. Selected Organic Syntheses: A Guidebook for Organic Chemists, John Wiley and Sons, 1973 (227 pages) Warren, S.; Organic Synthesis: The Disconnection Approach, John Wiley and Sons, 1982 (391 pages) Corey, E. J.; Cheng, X.-M. The Logic of Chemical Synthesis, John Wiley and Sons, 1989 (436 pages) Nicolaou, K. C.; Sorensen, E. J. Classics in Total Synthesis: Targets, Strategies, Methods, Wiley-Verlag, 1996 (798 pages) Functional Groups and Charge H 3 C X X = Cl, Br, I H 3 C OR R = H, Ms, Ts, Tf Alcohols and derivatives. This list is not exhaustive. halogens R 2 C O Since most carbon-carbon bond forming reactions are polar in nature, it is useful to classify Functional Groups with regard to the polarity they impose on carbon. For example, a halogen imposes partial positive charge on the carbon to which it is bonds. So does a hydroxyl group in the form of a mesylate (or many other derivatives). So does an oxygen that is doubly bonded to carbon (carbonyl compounds). These groups are all more electronegative than carbon. carbonyl compounds R 2 C NR imines Thus one can generate a set of Functional Groups that impart partial positive charge to carbon. Using terminology introduced by David Evans, I will call these E-functions (E for Electrophile).

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