For example, if you have one carbon in your molecule you plug one into your formula there, and you would get c1, and you would get 1 times 2 plus 2, which is of course 4, so ch4. As we know alkanes have a simple cc single bond in higher alkanes. Lecture 4 alkanes and cycloalkanes smart board free download as powerpoint presentation. This page deals briefly with the combustion of alkanes and cycloalkanes. Topic index previous next quiz clearance previous next quiz clearance. Combine the proper prefix, infix, and suffix, and write the iupac name for each compound. The iupac rules for naming alkanes are described in secs. Cyclopropane cl h hihd f i l id l b f liicyclopropane has a high degree of torsional strain due to large number of eclipsing interactions. It is quite important that you can write properly balanced equations for these reactions, because they often come up as a part of thermochemistry calculations. Practice naming hydrocarbons with branches and rings. More highly substituted cycloalkanes are named in a similar fashion, but care must be taken in numbering the ring. Ring strain is the higher potential energy of the cyclic form of a molecule compared to its acyclic form and is made up of angle strain and torsional strain. Alkanes and cycloalkanes chem 30a lecture 8 slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising.
The study of the energy changes that occur during these rotations is called conformational analysis. Substituents on a cycloalkane can be cis or trans to each other. We often refer to alkanes as aliphatic hydrocarbons, because the physi. Two chair conformations are possible for cis1,3dimethylcyclohexane.
Substituent names in alphabetical order and numbers are added prefixed to the base name of the compound. Cycloalkanes are named as per their acyclic counterparts with respect to the number of carbon atoms in their backbones, e. Fgs behave similarly in every molecule they are part of. Cyclic alkanes or cycloalkanes consist of hydrogen and carbon atoms bonded together with single bonds, where the carbon atoms bond together to form a ring or loop. You can bookmark this page if you like you will not be able to set bookmarks once you have. If you continue browsing the site, you agree to the use of cookies on this website. Alkyl groups, alkanes minus one hydrogen atom, are named similarly except that the ane ending is changed to yl. The chair conformation can be viewed as having two carbon atoms on the plane of the paper. Conformations of cycloalkanes cycloalkanes are not always planar structures. Uses of alkanes and cycloalkanes the uses of alkanes and cycloalkanes are defined by the carbon number. For saturated carbon chains alkanes the numbering system for the base carbon chain is determined by the positions of the substituents. In fact, there is very little difference between the two.
There is no such bond in methane, but ethane onwards all alkanes have a cc single bond. Course outcome ability to explain the relationship between the structure, physical and chemical properties of the different bonds and functional groups in organic compounds co2 course learning outcome the student should be able to. The conformations of ethane, butane, and cyclohexane are explained. Cycloalkanes are alkanes which have some of their carbon atoms arranged in a ring. Sch 102 introduction to organic chemistry, chemistry of alkanes. Two in another plane in front of the paper and the remaining two in a third plane. Alkanes all have the general molecular formula of cnh2n plus 2, where n is the number of carbons that are in your molecule. The two main natural sources of alkanes are natural gas and petroleum. Draw newman projections of alkanes in staggered and eclipsed conformations, and arrange the order of stability for these conformations conformational isomers. This conformation is lower in conforrmaciones and favored over the conformation with the methyl in the axial position. In this conformation, the distance between the bonds and the electrons in them is maximized. The removal of one h atom from cycloalkanes give rise to cycloalkyl radicals e. It deals with their formulae and isomerism, their physical properties, and an introduction to their chemical reactivity. Understanding alkanes and cycloalkanes universalclass.
Chapter 3 conformations of alkanes and cycloalkanes. As with alkanes, iupac rules specify a systematic nomenclature for naming cycloalkanes. The chemistry of the organic molecule is defined by the. Conformational analysis of ethane sawhorse cc h h h h h h hh h hh h 51 newman projection.
Cycloalkanes are hydrocarbons with a ringlike structure. Conformations of alkanes and cycloalkanes conformations of a molecule are different spatial arrangements of the atoms by simple rotation around carboncarbon single bonds. The following two cases provide examples of monosubstituted cycloalkanes. Write the structures of constitutional or structural isomers of alkanes. Conformational isomerism involves rotation about sigma bonds, and does not involve any differences in the connectivity or geometry of bonding. Three types include torsional, steric and angle conformation any 3d arrangement of atoms in a molecule that results from rotation about a single bond staggered conformation on a cc bond in. Notice that the parent name comes from the longest continuous carbon chain, which begins with the carbon of the ch 3 group at the bottom of the structural formula a and goes to the carbon of the ch 3 group on the top right side of the formula b. For the heat of combustion on the cycloalkanes, why isnt the number of ch2. The cyclo alkanes with small rings n 36 are of special interest in exhibiting chemical properties intermediate between those of alkanes and alkenes. Alkanes and cycloalkanes 11 million organic compounds which are classified into families according to structure and reactivity functional group fg. The lowest energy conformation of ethane, shown in the figure above, is called the staggered conformation, in which all of the ch bonds on the front carbon are positioned at dihedral angles of 60relative to the ch bonds on the back carbon. Substituents are named similar to the way they are. Lecture 4 alkanes and cycloalkanes smart board alkane.
In this context, saturated means that each carbon has the maximum number of hydrogens bonded to it. Learn how to recognize the alkane functional group in organic compounds. Conformational analysis of ethane sawhorse cc h h h h h. The chair conformation of cyclohexane is the most stable. For example, in hydrogen peroxide there are two conformations. Alkanes and cycloalkanes can be named by iupac or common nomenclature. Cycloalkanes do not all have the same relative stability. This molecule would have the general formula c4h10. Learn the iupac system for naming alkanes and cycloalkanes. Well be learning about different aspects of molecular structure, including common functional groups and conformations. Planar cyclopentane would have no angle strain but very high torsional strain actual conformations of cyclopentane are nonplanar, reducing torsional strain four carbon atoms are in a plane the fifth carbon atom is above or below the plane looks like an envelope.
They are commonly known as paraffins due to their less reactivity carbon is sp3 hybridised. Conformational isomers stereochemistry concerned with the 3d aspects of molecules rotation is possible around cc bonds in openchain molecules a conformation is one of the many possible arrangements of atoms caused by rotation about a single bond, and a specific conformation is called a conformer conformational. Jun 26, 2014 conformations of alkanes and cycloalkanes alkanes strain measure of energy stored in a compound due to a structural distortion. So this allows rotation of this single bonds to form a different spatial arrangement of carbon atoms, forming different conformations of such alkanes. A saturated hydrocarbon whose carbons are arranged in an open chain. Hydrocarbons, alkanes, and cycloalkanes will be defined. Classes of hydrocarbons molecules that are made up of carbon and hydrogen 1. Chapter 4 alkanes and cylcoalkanes chapter 4 alkanes and. An understanding of the forces at work and the energy associated with these processes is important because the structure of a molecule can have a significant influence on the molecular properties, including dictating the outcome of a reaction. Alkanes and cycloalkanes chapter 2 2 structure hydrocarbon. Lower members of cyclo alkanes are usually reported by simple geometrical drawing as etc. Shapes of alkanes all carbon atoms in alkanes and cycloalkanes are sp. Being planar requires large variations in bond angles from the ideal value of 109.
Applying the four nomenclature rules to the following compound. The products of both combusting stable and unstable alkane are the same. When a mixture of alkanes from the gas oil c 12 and higher fraction is heated at very high temperatures 500 o c in the presence of a variety of catalysts, the, the molecules break apart and rearrange to smaller, more highly branched alkanes containing 510 carbon atoms. C1 b c4 b natural gas, petroleum gas, c5 b c12 b motor fuel, c12 b c b kerosene, c15 b c25 b diesel, c16 c30 heavy oil, c25 b petroleum jelly or paraffin wax, and residue b asphalt. Alkanes, cycloalkanes, and functional groups khan academy.
Most reactions of organic compounds take place at or adjacent to a functional group. You should draw the ring in the plane of the paper solid lines and use dashes and wedges to show whether substitutents are above or below the plane of the ring. Cycloalkanes are drawn as simple polygons in which the sides represent the carboncarbon bonds. H oo h h oo h in this chapter we will learn how to draw molecules and we will study the relationship between the conformation and the energy. Conformations and cistrans stereoisomers stereochemistry. Alkane and cycloalkane nomenclature i video khan academy. Heat of combustion experiments illustrate that cyclohexane is the most stable cycloalkane see below. It has no torsional strain as all the ch bonds are staggered to each other. In order to establish a baseline of behavior against which these reactions may be ranked, we need to investigate the reactivity of compounds lacking any functional groups. Naming alkanes, cycloalkanes, and bicyclic compounds.
Cycloalkanes have two fewer hydrogen atoms than alkanes, because another carboncarbon bond is needed to form the ring. In order to form a ring, cycloalkanes are saturated, meaning they have at least three alkane compounds present to form a ring or a cycle. Rings of different sizes beginning with three carbons are possible. All the ch bonds are staggered in the chair conformation. The system is similar to that of alkanes but with a few subtleties. An introduction alkanes are aliphatic hydrocarbons having onl.
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