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.
7 Key excerpts on "Cycloalkanes"
eBook - ePub- Graham Patrick(Author)
- 2004(Publication Date)
- Taylor & Francis(Publisher)
...SECTION B — ALKANES AND Cycloalkanes B1 Definition Key Notes Alkanes Alkanes are organic molecules consisting solely of carbon and hydrogen atoms linked by single σ bonds. All the carbon atoms are tetrahedral and sp 3 hybridized. Alkanes are stable molecules and unreactive to most chemical reagents. They have the general formula C n H 2 n +2 Cycloalkanes Cycloalkanes are cyclic alkane structures. They have the general formula C n H 2 n. Most Cycloalkanes are unreactive to chemical reagents. However, three- and four-membered rings are reactive due to ring strain and behave like alkenes. Related topics (A3) sp 3 Hybridization (D4) Conformational isomers Alkanes Alkanes are organic molecules with the general formula C n H 2 n +2, which consist of carbon and hydrogen atoms linked together by C–C and C–H single bonds. They are often referred to as saturated hydrocarbons — saturated because all the bonds are single bonds, hydrocarbons because the only atoms present are carbon and hydrogen. All the carbon atoms in an alkane are sp 3 hybridized and tetrahedral in shape. The C–C and C–H bonds are strong σ bonds, and so alkanes are unreactive to most chemical reagents. Alkanes are sometimes referred to as straight chain or acyclic alkanes to distinguish them from Cycloalkanes or alicyclic compounds. Cycloalkanes Cycloalkanes are cyclic alkanes (alicyclic compounds) having the general formula C n H 2 n where the carbon atoms have been linked together to form a ring. All sizes of ring are possible. However, the most commonly encountered cycloalkane in organic chemistry is the six-membered ring (cyclohexane). Most Cycloalkanes are unreactive to chemical reagents. However, small three- and four-membered rings are reactive and behave like alkenes...
eBook - ePub- Jeffrey Gaffney, Nancy Marley(Authors)
- 2017(Publication Date)
- Elsevier(Publisher)
...The simple Cycloalkanes containing three to six carbon atoms are shown in Fig. 13.9. The structures shown in Fig. 13.9 are given in bonding notation and do not represent the actual structures of the molecules, which are not flat but are puckered in an attempt to achieve the109.5 degrees bonding angles of sp 3 hybridized alkanes. The smaller Cycloalkanes, cyclopropane and cyclobutane, have significant ring strain since the bond angles of 60 and 90 degrees are forced to be much smaller than 109.5 degrees. This makes them much less stable than the larger Cycloalkanes. Fig. 13.9 The chemical structure of the simplest Cycloalkanes containing three to six carbon atoms. Cyclic alkenes are also common, but only in larger ring sizes since the geometry of an sp 2 hybridized carbon is normally linear and smaller rings with very small bond angles would be extremely unstable. The cyclic alkenes have two sites of unsaturation, one from the double bond and one from the ring formation. Since they have lost a total of four hydrogens from the unsaturated alkane, they have the same molecular formula as the alkynes. So they are isomeric with the corresponding alkyne hydrocarbon having the same molecular formula. Another very important class of hydrocarbons is the aromatic hydrocarbons ; cyclic hydrocarbons composed of σ and π bonds are arranged in such a way that the electrons in the π bonds become delocalized giving the molecule unusual stability. Aromatic hydrocarbons originally received their name because many of the compounds have a sweet or pleasant odor. The simplest of the aromatic compounds is benzene, with a molecular formula of C 6 H 6. All of the benzene carbon atoms have sp 2 hybridization, so the molecular geometry is planar. Benzene is a cyclohexane ring with three double bonds alternated with three single bonds...
eBook - ePub- James G. Speight(Author)
- 2010(Publication Date)
- Gulf Professional Publishing(Publisher)
...Alkanes can have straight or branched chains, but without any ring structure. 2. Alkenes (olefins) are unsaturated hydrocarbons insofar as not all of the carbon valencies are satisfied by another atom and have a double bond (C=C) between carbon atoms. Alkenes have the general formula C n H 2 n, assuming no ring structures in the molecule. Alkenes may have more than one double bond between carbon atoms, in which case the formula is reduced by two hydrogen atoms for each additional double bond. For example, an alkene with two double bonds in the molecule has the general formula C n H 2 n – 2. Because of their reactivity and the time involved in crude oil maturation, alkenes do not usually occur in petroleum. 3. Alkynes (acetylenes) are hydrocarbons which contain a triple bond (C≡C) and have the general formula C n H 2 n – 2. Acetylene hydrocarbons are highly reactive and, as a consequence, are very rare in crude oil. 4. Cycloalkanes (naphthenes) are saturated hydrocarbons containing one or more rings, each of which may have one or more paraffinic side chains (more correctly known as alicyclic hydrocarbons). The general formula for a saturated hydrocarbon containing one ring is C n H 2 n. 5. Aromatic hydrocarbons (arenes) are hydrocarbons containing one or more aromatic nuclei, such as benzene, naphthalene, and phenanthrene ring systems, which may be linked up with (substituted) naphthene rings and/or paraffinic side chains. 5.1. Bonding in hydrocarbons Since carbon adopts the tetrahedral geometry when there are four σ bonds, only two bonds can occupy a plane simultaneously. The other two bonds are directed to the rear or to the front of the plane...
eBook - ePub- Christian Vargel(Author)
- 2020(Publication Date)
- Elsevier Science(Publisher)
...C 6 H 5 C 2 H 5 ; Ethylene, C 2 H 4 ; Ethylene, oxide, (CH 2) 2 O; Fatty acids; Fresh water; Heptane, C 7 H 16 ; Hexane, C 6 H 14 ; Hydrocarbons; Isobutane, C 4 H 10 ; Isoprene; Kerosene; Lime mud; Liquid natural gas (LNG); Methane, CH 4 ; Methyl esters; Microbiologically influenced corrosion (MIC); Naphthenes; Naphthalene, C 10 H 8 ; Octane, C 8 H 18 ; Paraffins; Pentane, C 5 H 12 ; Pinene; Propane; Propylene, C 3 H 6 ; Rubber; Seawater; Styrene, C 6 H 5 C 2 H 3 ; Sulphates; Terebenthine; Terphenyl,. C 6 H 5 C 6 H 4 C 6 H 5 ; Toluene, C 6 H 5 CH 3 ; Vegetable oils; Water; Xylene, C 6 H 4 (CH 3) 2 1.1 Alkanes 1.2 Alkenes 1.3 Alkynes 1.4 Arenes or aromatic hydrocarbons 1.5 Terphenyls 1.6 Cyclic, non-benzenic hydrocarbons 1.7 Engine fuels 1.7.1 Conventional fuels 1.7.2 Biofuels 1.8 Petroleum industry 1.9 Drilling muds References Hydrocarbons are the main constituents of crude oil and natural gas. They are used as fuels and lubricants and are the raw materials for the production of plastics, solvents and industrial chemicals. Hydrocarbons are organic chemical compounds composed only of carbon and hydrogen. Depending on how the carbon atoms are bonded together, hydrocarbons can be aliphatic or cyclic. The aliphatic compounds include alkanes (C n H 2n+2), alkenes (C n H 2n) and alkynes (C n H 2n − 2), depending on the number of unsaturated C–C bonds in the molecule. Cyclic compounds include aromatic hydrocarbons and cycloparaffins (non-benzenic hydrocarbons). Hydrocarbons are chemically relatively inert and, therefore, have no action on aluminium. They are insoluble in water. 1.1...
eBook - ePubWater Quality Data
Analysis and Interpretation
- Arthur Hounslow(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...CHAPTER 7 Organic Chemistry Nomenclature Introduction Organic compounds are composed primarily of variable numbers of carbon and hydrogen atoms, usually with smaller numbers of oxygen, nitrogen, sulfur, phosphorus, and halogen atoms—chlorine, fluorine, and bromine. Other elements may be incorporated in organic compounds to form organometallic compounds, but those will not be discussed here. Although specific references are generally not practical in this chapter, the text “Nomenclature of Organic Compounds” by Fletcher et al. (1974) was relied on extensively when nomenclature problems arose. The carbon atoms are joined to one another as chains, branched structures, or in rings. The carbon-carbon bonds may be single (sharing one electron pair), double (sharing two electron pairs), or triple (sharing three electron pairs). The most important ring structure, benzene, is one that consists of six carbon atoms and six hydrogen atoms in a planar ring. If a noncarbon atom replaces a carbon in a ring structure, the compound is called a heterocyclic compound. Most of the variation among organic compounds is caused by special groups of organic atoms attaching to the carbon atoms. They are called functional groups and contain at least one noncarbon atom. It is the presence of these groups that give organic compounds their unique properties. Organic compounds containing only carbon and hydrogen are called hydrocarbons. If they contain one or more halogen atoms they are called halogenated hydrocarbons. They may be divided into two groups, depending on whether the benzene ring is present or not. These are listed in Table 7.1. Early Organic Chemistry The term organic chemistry was originally used to designate those substances of plant and animal origin thought to be more closely related to one another than to subsiances of mineral origin. It was known that organic substances form CO 2 and H 2 0 when burned in air...
eBook - ePub- Tony Farine, Mark A. Foss(Authors)
- 2013(Publication Date)
- Routledge(Publisher)
...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. You may be unfamiliar with many of these, but if you have ever used a camping stove, you may be familiar with propane and butane as fuels. Petrol is a mixture of organic molecules, including alkanes. Chemical groups that are attached to a carbon-atom chain are called substituents. The simplest organic molecules result when carbon forms compounds with the substituent hydrogen alone. The resultant compounds are collectively referred to as hydrocarbons. Alkanes are examples of hydrocarbons, since they consist of hydrogen and carbon alone. Hydrocarbons Organic molecules that contain only single bonds between carbon atoms are said to be saturated. The group of aliphatic hydrocarbons (compounds containing only hydrogen and carbon in a straight chain) that are saturated are called alkanes, and they are named by adding the suffix –ane to the appropriate prefix. The simplest alkane is, therefore, methane. How many carbon atoms does methane possess? Remember those prefixes? If you do, you will have worked out that methane contains only one carbon atom (CH 4). Its structural formula is given in Figure 3.10. Perhaps you are already familiar with methane, since it is the main component of natural gas. You may also have used propane (C 3 H 8) and butane (C 4 H 10) as fuels in portable heaters and cookers. Take a moment to draw the structures of butane and propane. Now check your diagrams against Figure 3.10. Figure 3.10 The structural formulae of methane, butane and propane. Hydrocarbons that contain double or triple bonds are said to be unsaturated...
eBook - ePub- Michael North(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...Although the remainder of this chapter will focus on Cycloalkanes, the conformations of cyclic compounds containing heteroatoms in the ring are similar to those of the Cycloalkanes discussed here. For each ring system, in addition to discussion of the conformation of the unsubstituted ring, the influence that substituents on the ring have on the formation of both conformational and configurational stereoisomers will be surveyed. 8.4 Cyclopropane Since cyclopropane 8.11 is known to be a cyclic molecule, all of the C–C–C internuclear angles must equal 60° since the molecule has no choice but to adopt a conformation in which the three carbon atoms are coplanar and form an equilateral triangle. Hence, there is a large E θ since each of the C–C–C internuclear angles is distorted by almost 50°. In addition, all of the CH 2 groups eclipse one another (cf. the Newman projection 8.11a) so E ϕ is also large. This results in cyclopropane being a highly strained structure, although the experimental value (27.5 kcal mol −1, 115 kJ mol −1) for the strain energy is not as high as would have been predicted by Equation 8.1. Quantum mechanical calculations show that in cyclopropane, the carbon atoms do not hybridize their 2s and 2p orbitals to form sp 3 hybrid orbitals. Rather, the carbon–carbon bonds in cyclopropane actually have more p-character than if they were sp 3 hybridized, and since p-orbitals are orientated at 90° to one another, unlike the 109° 28′ orientation of sp 3 orbitals, this helps to relieve the strain present in the ring system...
