Chemistry
Cycloalkanes
Cycloalkanes are a class of organic compounds that contain a ring of carbon atoms. They are a subset of alkanes and are named based on the number of carbon atoms in the ring (e.g., cyclopropane, cyclobutane, cyclopentane). Cycloalkanes exhibit unique chemical and physical properties due to their ring structure, and they are commonly used as building blocks in organic synthesis.
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11 Key excerpts on "Cycloalkanes"
eBook - PDF- T. W. Graham Solomons, Craig B. Fryhle, Scott A. Snyder(Authors)
- 2017(Publication Date)
- Wiley(Publisher)
4.1 INTRODUCTION TO ALKANES AND Cycloalkanes 145 ▸ WHY DO THESE TOPICS MATTER? At the end of the chapter, we will show how, using the same set of rules, both chemists and nature have created some unique arrangements of carbon and hydrogen atoms. Some of these structural arrangements were not expected to exist, one structural arrangement lets you write, and others are fueling advances in the areas of novel materials research and nanotechnology. We noted earlier that the family of organic compounds called hydrocarbons can be divided into several groups on the basis of the type of bond that exists between the individual carbon atoms. Those hydrocarbons in which all of the carbon–carbon bonds are single bonds are called alkanes, those hydrocarbons that contain a carbon–carbon double bond are called alkenes, and those with a carbon–carbon triple bond are called alkynes. Cycloalkanes are alkanes in which all or some of the carbon atoms are arranged in a ring. Alkanes have the general formula C n H 2n+2 ; Cycloalkanes containing a single ring have two fewer hydrogen atoms and thus have the general formula C n H 2n . 4.1A Sources of Alkanes: Petroleum The primary source of alkanes is petroleum. Petroleum is a complex mixture of organic compounds, most of which are alkanes and aromatic compounds (cf. Chapter 14). It also contains small amounts of oxygen-, nitrogen-, and sulfur-containing compounds. Some of the molecules in petroleum are clearly of biological origin. Most scientists believe that petroleum originated with accumulation of dead microorganisms that settled to the bottom of the sea and that were entombed in sedimentary rock. These microbial remains eventually were transformed into oil by the heat radiating from Earth’s core. Hydrocarbons are also found in outer space. Asteroids and comets contain a variety of organic compounds. Methane and other hydrocarbons are found in the atmospheres of Jupiter, Saturn, and Uranus.
eBook - PDF- T. W. Graham Solomons, Craig B. Fryhle, Scott A. Snyder(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
4.1 INTRODUCTION TO ALKANES AND Cycloalkanes 145 [ WHY DO THESE TOPICS MATTER? ] At the end of the chapter, we will show how, using the same set of rules, both chemists and nature have created some unique arrangements of carbon and hydrogen atoms. Some of these structural arrangements were not expected to exist, one structural arrangement lets you write, and others are fueling advances in the areas of novel materials research and nanotechnology. See for additional examples, videos, and practice. We noted earlier that the family of organic compounds called hydrocarbons can be divided into several groups on the basis of the type of bond that exists between the individual carbon atoms. Those hydrocarbons in which all of the carbon–carbon bonds are single bonds are called alkanes, those hydrocarbons that contain a carbon–carbon double bond are called alkenes, and those with a carbon–carbon triple bond are called alkynes. Cycloalkanes are alkanes in which all or some of the carbon atoms are arranged in a ring. Alkanes have the general formula C n H 2n+2 ; Cycloalkanes containing a single ring have two fewer hydrogen atoms and thus have the general formula C n H 2n . 4.1A Sources of Alkanes: Petroleum The primary source of alkanes is petroleum. Petroleum is a complex mixture of organic compounds, most of which are alkanes and aromatic compounds (cf. Chapter 14). It also contains small amounts of oxygen-, nitrogen-, and sulfur-containing compounds. Some of the molecules in petroleum are clearly of biological origin. Most scientists believe that petroleum originated with accumulation of dead microorganisms that settled to the bottom of the sea and that were entombed in sedimentary rock. These microbial remains eventually were transformed into oil by the heat radiating from Earth’s core. Hydrocarbons are also found in outer space. Asteroids and comets contain a variety of organic compounds.
eBook - PDFChemistry for Today
General, Organic, and Biochemistry
- Spencer Seager, Michael Slabaugh, Maren Hansen, , Spencer Seager, Spencer Seager, Michael Slabaugh, Maren Hansen(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
According to IUPAC rules, Cycloalkanes are named by placing the prefix cyclo- before the name of the corresponding alkane with the same number of carbon atoms. Chemists often abbreviate the structural formulas for Cycloalkanes and draw them as geometric figures (triangles, squares, etc.) in which each corner represents a car- bon atom. The hydrogens are omitted (see Table 11.7). It is important to remember that each carbon atom still possesses four bonds, and that hydrogen is assumed to be bonded to the carbon atoms unless something else is indicated. When substituted cy- cloalkanes (those with attached groups) are named, the position of a single attached group does not need to be specified in the name because all positions in the ring are equivalent. However, when two or more groups are attached, their positions of attach- ment are indicated by numbers, just as they were for alkanes. The ring numbering begins with the carbon attached to the first group alphabetically and proceeds around the ring in the direction that will give the lowest numbers for the locations of the other attached groups. cycloalkane An alkane in which carbon atoms form a ring. Copyright 2022 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Organic Compounds: Alkanes 353 Example 11.9 Naming Cycloalkanes Represent each of the following Cycloalkanes by a geometric figure, and name each compound: CH H 2 C H 2 C H 2 C H 2 C CH 2 CH 3 CH CH 3 H 2 C H 2 C CH CH 3 CH 2 a. b. Solution a. A pentagon represents a five-membered ring, which is called cyclopentane.
eBook - PDF- William H. Brown, Thomas Poon(Authors)
- 2017(Publication Date)
- Wiley(Publisher)
• A carbon atom is classified as primary (1°), secondary (2°), tertiary (3°), or quaternary (4°), depending on the number of carbon atoms bonded to it. • A hydrogen atom is classified as primary (1°), secondary (2°), or tertiary (3°), depending on the type of carbon to which it is bonded. 3.4 What Are Cycloalkanes? • A cycloalkane is an alkane that contains carbon atoms bonded to form a ring. • To name a cycloalkane, prefix the name of the open‐chain hydrocarbon with “cyclo.” • Five‐membered rings (cyclopentanes) and six‐membered rings (cyclohexanes) are especially abundant in the bio- logical world. 3.5 What Is the IUPAC System of Nomenclature? • The IUPAC system is a general system of nomenclature. The IUPAC name of a compound consists of three parts: (1) A prefix that indicates the number of carbon atoms in the parent chain, (2) An infix that indicates the nature of the carbon–carbon bonds in the parent chain, and (3) A suffix that indicates the class to which the compound belongs. (4) Substituents derived from alkanes by the removal of a hydrogen atom are called alkyl groups and are given the symbol R. The name of an alkyl group is formed by dropping the suffix ‐ane from the name of the parent alkane and adding ‐yl in its place. 3.6 What Are the Conformations of Alkanes and Cycloalkanes? • A conformation is any three‐dimensional arrangement of the atoms of a molecule that results from rotation about a single bond. • One convention for showing conformations is the Newman projection. Staggered conformations are lower in energy (more stable) than eclipsed conformations.
- Frederick Bettelheim, William Brown, Mary Campbell, Shawn Farrell(Authors)
- 2019(Publication Date)
- Cengage Learning EMEA(Publisher)
Cycloalkane A saturated hydrocarbon that contains carbon atoms bonded to form a ring A petroleum fractional distillation tower. Marathon Petroleum Company, LLC FIGURE 11.2 Fractional distillation of petroleum. The lighter, more volatile fractions are removed from higher up the column; the heavier, less volatile fractions are removed from lower down. Crude oil and vapor are preheated Pipe still Gases Boiling point range below 20 ° C (C 1 –C 4 hydrocarbons; used as fuels and reactants to make plastics) Gasoline (naphthas) 20–200 ° C (C 5 –C 12 hydrocarbons; used as motor fuels and industrial solvents) Kerosene 175–275 ° C (C 12 –C 16 hydrocarbons; used for lamp oil, diesel fuel, starting material for catalytic cracking) Fuel oil 250–400 ° C (C 15 –C 18 hydrocarbons; used for catalytic cracking, heating oil, diesel fuel) Lubricating oil above 350 ° C (C 16 –C 20 hydrocarbons; used as lubricants) Residue (asphalt) ( H11022 C 20 hydrocarbons) 11.6 Cycloalkanes | 325 Copyright 2020 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Organic chemists rarely show all carbons and hydrogens when writing structural formulas for Cycloalkanes. Rather, we use line-angle formulas to represent cycloalkane rings and represent each ring by a regular polygon having the same number of sides as there are carbon atoms in the ring. For example, we represent cyclobutane by a square, cyclopentane by a penta-gon, and cyclohexane by a hexagon ( Figure 11.3 ). To name a cycloalkane, prefix the name of the corresponding open-chain alkane with cyclo-and name each substituent on the ring.
eBook - PDF- David R. Klein(Author)
- 2020(Publication Date)
- Wiley(Publisher)
This chapter will introduce only the most basic principles of conformational analysis, which we will use to analyze the flexibility of molecules. To simplify our discussion, we will explore compounds that lack a functional group, called alkanes and Cycloalkanes. Analysis of these compounds will enable us to understand how molecules achieve flexibility. Specifically, we will explore how alkanes and Cycloalkanes change their three-dimensional shape as a result of the rota- tion of C C single bonds. Our discussion of conformational analysis will involve the comparison of many different compounds and will be more efficient if we can refer to compounds by name. A system of rules for naming alkanes and Cycloalkanes will be developed prior to our discussion of molecular flexibility. 4.2 Nomenclature of Alkanes 133 4.1 INTRODUCTION TO ALKANES Recall that hydrocarbons are compounds comprised of only C and H; for example: C C H H H H H H Ethane C 2 H 6 C C H H H H Ethylene C 2 H 4 C C H H Acetylene C 2 H 2 Benzene C 6 H 6 Ethane is unlike the other examples in that it has no π bonds. Hydrocarbons that lack π bonds are called saturated hydrocarbons, or alkanes. The names of these compounds usually end with the suffix “-ane,” as seen in the following examples: Propane Butane Pentane This chapter will focus on alkanes, beginning with a procedure for naming them. The system of nam- ing chemical compounds, or nomenclature, will be developed and refined throughout the remaining chapters of this book. 4.2 NOMENCLATURE OF ALKANES An Introduction to IUPAC Nomenclature In the early nineteenth century, organic compounds were often named at the whim of their discover- ers.
eBook - ePub- Robert J. Ouellette, J. David Rawn(Authors)
- 2015(Publication Date)
- Elsevier(Publisher)
3Alkanes and Cycloalkanes
Hydrocarbons, as their names indicates, contain only hydrogen and carbon. They occur as mixtures in natural gas, petroleum, and coal, which are collectively known as fossil fuels since they contain the remnants (fossils) of ancient organisms, including plants, animals, and microorganisms that have been buried for millions of years at high temperature and pressure under anaerobic conditions.Hydrocarbons fall into two broad classes based on the types of bonds between the carbon atoms. A hydrocarbon that has only carbon-carbon single bonds is saturated . Hydrocarbons that contain carbon-carbon multiple bonds are unsaturated . Alkanes and Cycloalkanes are two types of saturated hydrocarbons. Alkanes have carbon atoms bonded in chains; Cycloalkanes have carbon atoms bonded to form a ring.3.1 Classes of Hydrocarbons
Compounds that have a chain of carbon atoms, some of which are attached to functional groups, are called acyclic compounds, meaning “not cyclic.” Compounds that contain rings of carbon atoms, and that may also contain functional groups, are carbocyclic compounds, commonly called Cycloalkanes. One example is cyclobutane, which is shown below. Some cyclic compounds contain at least one atom in the ring other than carbon; those atoms are called heteroatoms . Cyclic compounds containing one or more heteroatoms are called heterocyclic compounds. The structures of an acyclic compound 2-heptanone, a carbocyclic compound, carvone, and the heterocyclic compound nicotinic acid are shown below.Aromatic rings, which we briefly introduced in Chapter 2 , are also “hydrocarbons,” but they are an entirely different class of compounds, which we will discuss in Chapter 4 .3.2 Alkanes
Hydrocarbons that have no carbon-carbon double or triple bonds are called saturated hydrocarbons . They have a continuous chain of carbon atoms, and do not have any “branches.” They are called normal alkanes
eBook - PDF- David R. Klein(Author)
- 2016(Publication Date)
- Wiley(Publisher)
Our discussion of conformational analysis will involve the comparison of many different compounds and will be more efficient if we can refer to compounds by name. A system of rules for naming alkanes and Cycloalkanes will be developed prior to our discussion of molecular flexibility. 4.1 Introduction to Alkanes 4.2 Nomenclature of Alkanes 4.3 Constitutional Isomers of Alkanes 4.4 Relative Stability of Isomeric Alkanes 4.5 Sources and Uses of Alkanes 4.6 Drawing Newman Projections 4.7 Conformational Analysis of Ethane and Propane 4.8 Conformational Analysis of Butane 4.9 Cycloalkanes 4.10 Conformations of Cyclohexane 4.11 Drawing Chair Conformations 4.12 Monosubstituted Cyclohexane 4.13 Disubstituted Cyclohexane 4.14 cis-trans Stereoisomerism 4.15 Polycyclic Systems 4 4.2 Nomenclature of Alkanes 133 4.1 Introduction to Alkanes Recall that hydrocarbons are compounds comprised of only C and H; for example: C C H H H H H H Ethane C 2 H 6 C C H H H H Ethylene C 2 H 4 C C H H Acetylene C 2 H 2 Benzene C 6 H 6 Ethane is unlike the other examples in that it has no π bonds. Hydrocarbons that lack π bonds are called saturated hydrocarbons, or alkanes. The names of these compounds usually end with the suffix “-ane,” as seen in the following examples: Propane Butane Pentane This chapter will focus on alkanes, beginning with a procedure for naming them. The system of nam- ing chemical compounds, or nomenclature, will be developed and refined throughout the remaining chapters of this book. 4.2 Nomenclature of Alkanes An Introduction to IUPAC Nomenclature In the early nineteenth century, organic compounds were often named at the whim of their discover- ers.
eBook - PDF- H. Stephen Stoker(Author)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
Figure 1-6 Three-dimensional representations of the structures of simple Cycloalkanes. a Cyclopropane, C 3 H 6 b Cyclobutane, C 4 H 8 c Cyclopentane, C 5 H 10 d Cyclohexane, C 6 H 12 ▶ Cycloalkanes, unlike alkanes, have no end carbons. Hence, they always have two fewer hydro-gen atoms than corresponding alkanes. Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 26 CHAPTER 1 Saturated Hydrocarbons The observed C ! C ! C bond angles in cyclopropane are 60°, and those in cyclobutane are approximately 90°, values that are considerably smaller than the 109° angle associated with a tetrahedral arrangement of bonds about a carbon atom. Consequently, cyclopropane and cyclobutane are relatively unstable compounds. Five- and six-membered cycloalkane structures are much more stable, and these structural entities are encountered in many organic molecules. Generating Condensed Structural Formulas from Line-Angle Structural Formulas for Cycloalkanes Generate the condensed structural formula for each of the following Cycloalkanes. a. b. Solution a. First replace each angle and line terminus with a carbon atom, and then add hydro-gens as necessary to give each carbon four bonds. The molecular formula of this compound is C 8 H 16 . C C C C C C C C H 2 C H 2 C CH 2 CH 3 CH 3 CH 2 CH CH b. Similarly, we have C C C C C C C C CH 3 CH 3 CH 2 CH 2 CH CH H 2 C H 2 C E X A M PL E 1 -6 1. When the molecular formulas for cyclic and noncyclic alkanes with the same number of carbon atoms are compared, it is always found that the cycloalkane has a.
- David R. Klein(Author)
- 2017(Publication Date)
- Wiley(Publisher)
Chapter 4 Alkanes and Cycloalkanes Review of Concepts Fill in the blanks below. To verify that your answers are correct, look in your textbook at the end of Chapter 4. Each of the sentences below appears verbatim in the section entitled Review of Concepts and Vocabulary. Hydrocarbons that lack ____________ are called saturated hydrocarbons, or ___________. _________________ provide a systematic way for naming compounds. Rotation about C-C single bonds allows a compound to adopt a variety of __________________. ___________ projections are often used to draw the various conformations of a compound. _____________ conformations are lower in energy, while ____________ conformations are higher in energy. The difference in energy between staggered and eclipsed conformations of ethane is referred to as _____________ strain. ________ strain occurs in Cycloalkanes when bond angles deviate from the preferred _____°. The _______ conformation of cyclohexane has no torsional strain and very little angle strain. The term ring flip is used to describe the conversion of one ____________ conformation into the other. When a ring has one substituent…the equilibrium will favor the chair conformation with the substituent in the _____________ position. Review of Skills Fill in the blanks and empty boxes below. To verify that your answers are correct, look in your textbook at the end of Chapter 4. The answers appear in the section entitled SkillBuilder Review. SkillBuilder 4.1 Identifying the Parent SkillBuilder 4.2 Identifying and Naming Substituents SkillBuilder 4.3 Identifying and Naming Complex Substituents CHAPTER 4 103 SkillBuilder 4.4 Assembling the Systematic Name of an Alkane SkillBuilder 4.5 Assembling the Name of a Bicyclic Compound SkillBuilder 4.6 Identifying Constitutional Isomers SkillBuilder 4.7 Drawing Newman Projections SkillBuilder 4.8 Identifying Relative Energy of Conformations
eBook - PDF- William H. Brown, Thomas Poon(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
To perform a chair‐to‐ chair interconversion, change the orientation of the rightmost and leftmost carbons in the chair conformation of cyclohexane. Remember that after such an interconversion, all prior axial substituents become equatorial and all prior equatorial substitu- ents become axial. When converting to planar representations of cyclohexane, show substituents above the ring as coming out of the page (wedges) and those below the ring as going behind the page (dashes). S O L U T I O N (a) The isomer shown is cis‐1,3‐dimethylcyclohexane; the two methyl groups are on the same side of the ring. (b) CH 3 CH 3 H H CH 3 CH 3 H H (less stable) (more stable) a chair-to-chair interconversion will never change the cis or trans relationship between two substituents. That is, cis will remain cis and trans will remain trans 3.8 What Are the Physical Properties of Alkanes and Cycloalkanes? The most important property of alkanes and Cycloalkanes is their almost complete lack of polarity. As we saw in Section 1.2C, the difference in electronegativity between carbon and hydrogen is 2 5 2 1 0 4 . . . on the Pauling scale, and given this small difference, we classify a C H bond as nonpolar covalent. Therefore, alkanes are nonpolar compounds, and there are only weak interactions between their molecules. Pentane Cyclohexane Pentane and cyclohexane. The electron density models show no evidence of any polarity in alkanes and Cycloalkanes. A. Boiling Points The boiling points of alkanes are lower than those of almost any other type of compound with the same molecular weight. In general, both boiling and melting points of alkanes increase with increasing molecular weight (Table 3.4). Alkanes containing 1 to 4 carbons are gases at room temperature, and those contain- ing 5 to 17 carbons are colorless liquids. High‐molecular‐weight alkanes (those with 18 or more carbons) are white, waxy solids. Several plant waxes are high‐molecular‐weight alkanes.
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