Alkanes are organic compounds that consist entirely of singlebonded carbon and hydrogen atoms and lack any other functional groups. Structure and stereochem slide 319 reactions of alkanes combustion complete oxidation of an organic molecule in the presence of oxygen. Name the longest straight unbranched carbon chain in the structure. Simply put, aliphatic compounds are compounds that do not incorporate any aromatic rings in their molecular structure.
If there are several groups of the same kind, list the group only once, using. Alkanes and alkyl groups can be subclassified as aliphatic acyclic or cycloaliphatic based on their general structure. Preceding the name of the longest chain, write down in alphabetical order the names of each of the alkyl groups which are attached to the main chain. Principles of drug action 1, spring 2005, alkanes 1 hydrocarbon structure and chemistry. As these bonds are all single bonds, there is free rotation around all connections. An eightcarbon alkane has a molecular formula c 8h 18 and structural formulaalkanes list. Carbons in the middle of a chain are attached to two hydrogens. Alkane and cycloalkane nomenclature ii our mission is to provide a free, worldclass education to anyone, anywhere. Chapter 3 22 melting points of alkanes branched alkanes pack more efficiently into a crystalline structure, so have higher m. For alkenes, alkynes and aromatic hydrocarbons, spring models can be constructed. The ability of carbon atoms to form strong, stable bonds with other. Each of the carbon atoms in an alkane has sp 3 hybrid orbitals and is bonded to four other atoms, each of which is either carbon or hydrogen. Alkanes chemical nomenclature assigns compounds a unique name that allows them to be easily identified and structurally understood. Methane gas is the first member of the homologous series of alkanes.
Learn the important physical and chemical properties of the alkanes. Alkanes are rarely prepared from other types of compounds because of economic reasons. Groups that are cis on the alkene will end up cis on the cyclopropane product. As such, the geometry of the alkene is preserved in the product. Draw the structural formula and line angle formula for the following molecules. Collectively, they are called unsaturated hydrocarbons because they have fewer hydrogen atoms than does an alkane with the same number of carbon atoms. This chapter describes the skeleltal isomerism of alkanes and cycloalkanes, their threedimensional conformations, and their systematic nomenclature that is the basis for the names of all other organic compounds. Learn how to recognize the alkane functional group in organic compounds. Alkane structure, properties and examples chemistry dictionary. Simply put, aliphatic compounds are compounds that do not incorporate any.
Well, of course, theres one, two, and three carbons. Cyclic structure containing heteroatoms are called heterocyclic. The lewis structures and models of methane, ethane, and pentane are illustrated in figure \\pageindex1\. Structures and names of alkanes chemistry libretexts. Alkanes, or saturated hydrocarbons, contain only single covalent bonds between carbon atoms. In structures ii, iv and v, you observed that ch3 group is attached to carbon atom numbered as 2. We begin our study of organic chemistry with the hydrocarbons, the simplest organic compounds, which are composed of carbon and hydrogen atoms only. The list of some alkanes and the molecular formula is given below. Identify the longest continuous carbon chain as the parent chain. Thus, given the number of carbon atoms in an alkane, it is easy to determine the number of hydrogens in the molecule.
Members of a group of compounds, such as the alkanes, that have simi lar chemical structures and graded physical properties, and which differ from. Apr 04, 2018 introduction to alkane alkanes are saturated hydrocarbon consist of carbon and hydrogen only without any functional group. Structure of alkenes 8 cis,trans isomerism in alkenes cis,trans isomers. If more than one different chains are of equal length number of carbons, choose the one with the greater number of branch points. This chapter begins with the study of the simplest organic molecules. Draw conformations of alkanes and cycloalkanes when given the name, and identify conformations when given a structure.
Alkane and cycloalkane nomenclature i video khan academy. Perfect for acing essays, tests, and quizzes, as well as for writing lesson plans. Structure and stereochemistry of alkanes organic chemistry, 5th edition l. The double bond makes alkenes more reactive than alkanes. Since we are naming alkanes, our first role is to identify the longest chain. Chapter 3 structure and stereochemistry of alkanes. Structural isomers just how many structures can you make from a simple formula. Unsaturated hydrocarbons have double or triple bonds and are quite reactive. C2h6 once the two carbons are connected, there are only six additional bonding sites and these are filled by the six hydrogen atoms.
Molecular and structural formulas the alkanes comprise a series of compounds that are composed of carbon and hydrogen atoms with single covalent bonds. The earliest nomenclature systems followed almost no systematic rules. Since all alkanes are similar in structure and properties, they are called a homologous series. The cf bond is much more resistant to uv light than the ccl bond. If a noncyclic alkane contains 15 carbon atoms, how many hydrogen atoms does it contain. Structure and nomenclature chapter 5 2 unsaturated hydrocarbon. Pdf effect of chemical structure on secondary organic. Introduction hydrocarbons are organic compounds consisting of cc and ch bonds.
Draw structural formulas for the three constitutional isomers with molecular formula c5h12. Structural isomers just how many structures can you make. Fgs behave similarly in every molecule they are part of. Pdf chapter 3 structure and stereochemistry of alkanes. In an alkane, all 4 4 4 valencies of the carbon atom are satisfied with other hydrogen atoms. Classification of alkane there are three types of alkanes. Within alkane structure there is free rotation about the carbontocarbon single bonds. The following table lists the iupac names assigned to simple continuouschain alkanes from c1 to c10. Although many different types of nomenclature, or naming systems, were employed in the past, today only the international union of pure and applied chemistry iupac nomenclature is acceptable for all scientific publications. Name the molecules below are there geometric isomers of the above two structures. Now lets go with more advanced examples and lets apply all iupac rules to get the name.
Molecular and structural formulas the alkynes comprise a series of carbon. In addition to our examination of alkanes, we will also take a brief look. Physical properties of alkanes alkanes are nonpolar only dispersion forces act between molecules. Yet another representation of molecular structural formulas. Draw the structure of an alkane when given its name. If you have fluorine coming off of the carbon chain, it is named as fluoro. Chapter 3 2 alkane formulas four carbonor hydogen atoms bonded to each carbon atom all cc single bonds ratio. Boiling points, melting points, and densities generally increase with the size of the alkane. Alkanes and cycloalkanes 11 million organic compounds which are classified into families according to structure and reactivity functional group fg. The simplest alkane, methane, has one carbon atom and a molecular formula of ch 4. Aromatic hydrocarbons contain the 6membered benzene ring structure a that is characterized by alternating double bonds. Ch4 c h h h h ch4 c h h condensed formula 2d formula 3d formula methane 2. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carboncarbon bonds are single. We will include compounds which contain a c bonded to a halogen also c1, f, br, i.
Contains a carboncarbon double bond and has the general formula c nh 2n. Alkanes formula, definition, structure, properties. Aromatic hydrocarbons are defined by having 6membered ring structures with alternating double bonds fig 8. The base name of cycloalkanes is based on the greek for the number of carbons in the ring with the prefix cyclo and the suffix ane. Aug 12, 2019 to identify and name simple straightchain alkanes given formulas and write formulas for straightchain alkanes given their names. When it comes to halogens, you have to change the ending ine to o. Learn exactly what happened in this chapter, scene, or section of organic chemistry. An eightcarbon alkane has a molecular formula c 8h 18 and structural formula alkanes list.
Another shorthand representation of alkanes the bondline formula. Alkanes are organic compounds containing carbon and hydrogen with single bonds only. Alkanesandalkenesworksheet how can we distinguish between alkanes and alkenes. However, ignoring financial considerations, alkanes can be prepared from. Cycloalkanes are alkanes arranged in a cyclic structure. Learn how to write condensed, expanded, and line structures for organic compounds. Since all alkanes are similar in structure and properties, they are called a homologous series the structure of an alkane, as with all hydrocarbons, can be represented with a. Well be learning about different aspects of molecular structure, including common functional groups and conformations. When the chain is longer than 3 carbons, number the atoms such that the double bond is given the lowest number i. Organic molecules are often organized by structures called functional groups, which are characteristic arrangement of atoms which define many of the physical and chemical properties of a class of organic compounds.
Alkane names are based on the number of carbon atoms. What is the general formula for a noncyclic alkane. The properties of organic molecules depend on the structure, and knowing the names of organic compounds allow us to communicate with other chemists. They are unsaturated compounds with at least one carbontocarbon double bond. Their adjacent atoms are connected with sigma bonds and form tetrahedral centers around the carbon atoms. Of the hydrocarbons, the most basic molecules are alkanes, which consist of only single bonds. Isomers that have the same connectivity but a different arrangement of their atoms in space due to the presence of either a ring chapter 2 or a carboncarbon double bond. If you go on constructing structures for higher alkanes, you will be getting still larger number of isomers. Alkene nomenclature please read and understand prefixparentsuffix suffix for alkenes. As noted before, alkenes are hydrocarbons with carbontocarbon double bonds r 2 ccr 2 and alkynes are hydrocarbons with carbontocarbon triple bonds rc. Effect of chemical structure on secondary organic aerosol formation for c12 alkanes article pdf available in atmospheric chemistry and physics 4. Ch 3 ch ch ch 2 ch 2 ch 2 ch 2 ch 3 ch 3 ch 3 7 carbons heptb. What is the systematic name for the following structure. For making models of alkanes, you can use toothpicks for bonds and plasticine balls for atoms.
Aliphatic alkanes are linear or branched structures as shown in the example above. Branched alkanes normally exhibit lower boiling points than unbranched alkanes of the same carbon content. These carbon atoms already have four electrons, but they each want to get four more so that they have a full eight in the valence shell. The alkanes and cycloalkanes are also members of a larger class of compounds referred to as. The base name of alkanes is derived from the greek for the number of carbons in the longest continuous carbon chain table 2. Alkanes, cycloalkanes, and functional groups khan academy. The physical properties of alkenes are similar to those of the alkanes. Cycloaliphatics or cycloalkanes contain the alkane or alkyl fragment as part of a carbon cycle. Elimination reactions alkenes olefins are hydrocarbons that contain a carboncarbon double bond and are said to be unsaturated. Ultradur, pbt is a plastic polymer that contains an aromatic functional group. Usually there is too great a variation in molecular structure for regularities to be apparent. In organic chemistry, an alkane, or paraffin a historical name that also has other meanings, is an acyclic saturated hydrocarbon.
If you observe the structure, three types of chains are possible two chains each with 6 carbons and another chain with 5. Draw the line bond structures of following types of hydrocarbons using four carbon atoms. In this system, a series of rules has been created that is adaptable to all classes of organic compounds. A hydrocarbon molecule contains only carbon and hydrogen. Ethene an alkene h c c h h h unsaturated hydrocarbons. Alkanes can be subdivided into the following three groups. Monocyclic alkanes with no side chains are named similarly to acyclic alkanes, but with the prefix cycloattached to the parent hydride name e. Learn the iupac system for naming alkanes and cycloalkanes. However, ignoring financial considerations, alkanes can be prepared from the following compounds. For substituted and unsubstituted cyclohexanes, the most important conformation is the chair. If you are an advanced reader, you can jump to examples given at the end of this article. Alkanes formula, definition, structure, properties, videos. This group of compounds is a homologous series with the general molecular formula of c n h 2 n 2, where n equals any integer greater than one. Alkane names, formulas, properties memorize sections 3.
To work out the best way to distinguish alkanes from alkenes. The simplest of the functional groups are the hydrocarbons, which include the alkanes. Each atom is attached to the sufficient hydrogen atoms to develop a total of four single covalent bonds. Notice that both of these molecules contain only f halogen atoms and no cl atoms. Molecular and structural formula of alkanes youtube. They consist of the elements carbon and hydrogen, and all the bonds between the carbon atoms are single bonds. Organic chemistry is concerned with the study of the structure and properties of compounds containing carbon. The cyclopropanation reaction of an alkene with a carbene takes place in a single step. Boiling points of alkanes branched alkanes have less surface area contact, so weaker intermolecular forces. Alkanes are the saturated hydrocarbons without any functional group so iupac naming is somewhat easy so, lets go with simple examples initially and then to more advanced structures of alkanes. Since alkanes are the most fundamental types of organic compounds, their structural features a basic carbon chain, or skeleton provide the basis for the nomenclature of all organic compounds. The alkanes and cycloalkanes are also members of a larger class of compounds referred to as aliphatic. For butane and related molecules, the important conformations are eclipsed and staggered including gauche and anti. Carbon has a valence of four and thus requires four electrons or bonds to complete its octet in the neutral state.
Alkanes that have carbons that are bonded to more than 2. Groups that are trans on the alkene will end up trans on the cyclopropane product. The international union of pure and applied chemistry iupac is the organization that assigns names to chemical compounds, and these names generally have three. Alkanes are less dense than water and swim on top of water.
Structural formulas division of the family of hydrocarbons visualization of an alkanes structure alkanes acetylene cycloparaffins alcohol. Alkanes, hydrocarbons, class 11 the acyclic saturated hydrocarbons are called paraffins since they are relatively unreactive towards most of the reagents such as acids, bases oxidizing and reducing agents. A halogen is also treated as a substituent when it comes to naming alkanes. Microsoft word practice problems on alkane nomenclature. Jul 30, 2018 alkanes, hydrocarbons, class 11 the acyclic saturated hydrocarbons are called paraffins since they are relatively unreactive towards most of the reagents such as acids, bases oxidizing and reducing agents. Identify each as an alkane, an alkene, or an alkyne. Hydrocarbons are further divided into several structural types called, alkanes, alkenes, alkynes and. Branchedchain alkanes do not exhibit the same smooth gradation of physical properties as do the continuouschain alkanes. Carbons on the end of a chain are attached to three hydrogens. Hfa 4a has the structure and the systematic name 1,1,1,2tetrafluoroethane hfa 227 has the wedge and dash structure and the systematic name 1,1,1,2,3,3,3heptafluoropropane.