{"id":517,"date":"2017-10-04T20:55:19","date_gmt":"2017-10-04T20:55:19","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/?post_type=chapter&p=517"},"modified":"2018-10-03T17:17:41","modified_gmt":"2018-10-03T17:17:41","slug":"nomenclature-of-cycloalkanes","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-mcc-organicchemistry\/chapter\/nomenclature-of-cycloalkanes\/","title":{"raw":"Nomenclature of Cycloalkanes","rendered":"Nomenclature of Cycloalkanes"},"content":{"raw":"
\u00a0Cycloalkanes are cyclic hydrocarbons<\/a>, meaning that the carbons of the molecule are arranged in the form of a ring. Cycloalkanes are also saturated, meaning that all of the carbons atoms that make up the\u00a0ring\u00a0are single bonded to other atoms (no double or triple bonds). There are also polycyclic alkanes, which are molecules that contain two or more cycloalkanes\u00a0that are joined, forming multiple rings.<\/div>\r\n
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Introduction<\/h3>\r\nMany organic compounds found in nature or created in a laboratory contain rings of carbon atoms with distinguishing chemical properties; these compounds are known as cycloalkanes. Cycloalkanes only contain carbon-hydrogen bonds and carbon-carbon single bonds, but\u00a0in cycloalkanes,\u00a0the carbon atoms are joined in a ring. The smallest cycloalkane is cyclopropane.\r\n

\"image\"<\/p>\r\nIf you count the carbons and hydrogens, you will see that they no longer fit the general formula $$C_nH_{2n+2}$$. By joining the carbon atoms in a ring,two hydrogen atoms have been lost. The general formula for a cycloalkane is $$C_nH_{2n}$$. Cyclic compounds are not all flat molecules. All of the cycloalkanes, from cyclopentane upwards, exist as \"puckered rings\". Cyclohexane, for example, has a ring structure\u00a0that looks like this:\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"120\"]\"image\" Figure 2: This is known as the \"chair\" form of cyclohexane from its shape, which vaguely resembles a chair. Note: \u00a0The cyclohexane molecule is constantly changing, with the atom on the left, which is currently pointing down, flipping up, and the\u00a0atom on the right flipping down. During this process, another (slightly less stable) form of cyclohexane is formed known as the \"boat\" form. In this arrangement, both of these atoms are either pointing up or down at the same time[\/caption]\r\n\r\nIn addition to being saturated cyclic hydrocarbons, cycloalkanes may have multiple substituents or functional <\/a>groups <\/a>that further determine their unique chemical properties. The most common and useful cycloalkanes in organic chemistry are cyclopentane and cyclohexane, although other cycloalkanes varying in the number of carbons can be synthesized. Understanding cycloalkanes and their properties are crucial in that many of the biological processes that occur in most living things have cycloalkane-like structures.\r\n\r\n\r\n\r\n\r\n
\"drawing012.gif\"<\/td>\r\n\"drawing013.gif\"<\/td>\r\n\"cholesterol.gif\"<\/td>\r\n<\/tr>\r\n
Glucose <\/a>(6 carbon sugar)<\/td>\r\nRibose <\/a>(5 carbon sugar)<\/td>\r\nCholesterol <\/a>(polycyclic)<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nAlthough polycyclic compounds are important, they are\u00a0highly complex and typically have common names accepted by IUPAC. However, the common names do not generally follow the basic IUPAC nomenclature rules. The general formula of the cycloalkanes is $$C_nH_{2n}$$ where $$n$$ is the number of carbons. The naming of cycloalkanes follows a simple set of rules\u00a0that are built upon the same basic steps in naming alkanes<\/a>. Cyclic hydrocarbons have the prefix \"cyclo-\".\r\n\r\n<\/div>\r\n
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Contents<\/h3>\r\nFor simplicity, cycloalkane molecules can be drawn in the form of skeletal structures\u00a0in which\u00a0each intersection between two lines\u00a0is assumed to have a carbon atom with its corresponding number of hydrogens.\r\n\r\n\"2\u00a0\u00a0\u00a0 same as\u00a0\u00a0\u00a0\u00a0\"4.gif\"\u00a0\u00a0\u00a0 same as \u00a0\u00a0\u00a0\"cyclohexane.gif\"\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Cycloalkane<\/strong><\/td>\r\nMolecular Formula<\/strong><\/td>\r\nBasic Structure<\/strong><\/td>\r\n<\/tr>\r\n
Cyclopropane<\/td>\r\nC3<\/sub>H6<\/sub><\/td>\r\n\"cyclopropane.gif\"<\/td>\r\n<\/tr>\r\n
Cyclobutane<\/td>\r\nC4<\/sub>H8<\/sub><\/td>\r\n\"cyclobutane.gif\"<\/td>\r\n<\/tr>\r\n
Cyclopentane<\/td>\r\nC5<\/sub>H10<\/sub><\/td>\r\n\u00a0\"cyclopentane.gif\"<\/td>\r\n<\/tr>\r\n
Cyclohexane<\/td>\r\nC6<\/sub>H12<\/sub><\/td>\r\n\u00a0\"cyclohexane.gif\"<\/td>\r\n<\/tr>\r\n
Cycloheptane<\/td>\r\nC7<\/sub>H14<\/sub><\/td>\r\n\u00a0\"cycloheptane.gif\"<\/td>\r\n<\/tr>\r\n
Cyclooctane<\/td>\r\nC8<\/sub>H16<\/sub><\/td>\r\n\u00a0\"cyclooctane.gif\"<\/td>\r\n<\/tr>\r\n
Cyclononane<\/td>\r\nC9<\/sub>H18<\/sub><\/td>\r\n\u00a0\"cyclononane.gif\"<\/td>\r\n<\/tr>\r\n
Cyclodecane<\/td>\r\nC10<\/sub>H20<\/sub><\/td>\r\n\u00a0\"cyclodecane.gif\"<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n
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IUPAC Rules for Nomenclature<\/h3>\r\n
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  1. Determine the cycloalkane to use as the\u00a0parent chain. The parent chain is the one with the highest number of carbon atoms. If there are two cycloalkanes, use the cycloalkane with\u00a0the higher number of\u00a0carbons as the parent chain.<\/li>\r\n \t
  2. If there is an alkyl straight chain that\u00a0has a\u00a0greater number of carbons than the cycloalkane, then the alkyl chain must be used as the primary parent chain. Cycloalkane acting as a substituent to an alkyl chain has an ending \"-yl\" and, therefore, must be named as a cycloalkyl.<\/li>\r\n<\/ol>\r\n
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    Examples<\/h3>\r\n\"drawing020.gif\"\r\n\r\nThe longest straight chain contains 10 carbons, compared\u00a0with cyclopropane, which only contains 3 carbons.\u00a0Because cyclopropane is a substituent, it would be named a cyclopropyl-substituted alkane.\r\n\r\n<\/div>\r\n \r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Cycloalkane<\/strong><\/td>\r\nCycloalkyl<\/strong><\/td>\r\n<\/tr>\r\n
    cyclopropane<\/td>\r\ncyclopropyl<\/td>\r\n<\/tr>\r\n
    cyclobutane<\/td>\r\ncyclobutyl<\/td>\r\n<\/tr>\r\n
    cyclopentane<\/td>\r\ncyclopentyl<\/td>\r\n<\/tr>\r\n
    cyclohexane<\/td>\r\ncyclohexyl<\/td>\r\n<\/tr>\r\n
    cycloheptane<\/td>\r\ncycloheptyl<\/td>\r\n<\/tr>\r\n
    cyclooctane<\/td>\r\ncyclooctyl<\/td>\r\n<\/tr>\r\n
    cyclononane<\/td>\r\ncyclononanyl<\/td>\r\n<\/tr>\r\n
    cyclodecane<\/td>\r\ncyclodecanyl<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n \r\n\r\n3) Determine any functional groups<\/a> or other alkyl groups.\r\n\r\n4) Number the carbons of the cycloalkane so that the carbons with functional groups or alkyl groups have the lowest possible number. A carbon with multiple substituents should have a lower number than a carbon with only one substituent or functional group. One way to make sure that the lowest number possible is assigned\u00a0is to number the carbons so that when the numbers corresponding to the substituents are added,\u00a0their sum is the lowest possible.\r\n

    \"drawing01(1+3=4)\u00a0\u00a0\u00a0\u00a0NOT<\/strong> \u00a0\u00a0 \"drawing02(1+5=6)<\/p>\r\n5) When naming the cycloalkane, the\u00a0substituents and functional groups must be placed\u00a0in alphabetical order.\r\n\r\n\"noname20.gif\"\u00a0\u00a0\u00a0 \"drawing03.gif\"\r\n\r\n(ex: 2-bromo-1-chloro-3-methylcyclopentane)\r\n\r\n6) Indicate the carbon number with the functional group with the highest priority according to alphabetical order. A dash\"-\" must be placed between the numbers and the name of the substituent.\u00a0 After the carbon number and the dash, the name of the substituent can follow.\u00a0 When there is only one substituent on the parent chain,\u00a0indicating\u00a0the number of the carbon atoms with the substituent is not necessary.\r\n\r\n(ex: 1-chlorocyclohexane or cholorocyclohexane is acceptable) \"drawing3.gif\"\r\n\r\n7) If there is more than one of the same functional group on one carbon, write the number of the carbon two, three, or four times, depending on how many of the same functional group is present on that carbon.\u00a0 The numbers must be separated by commas, and the name of the functional group that follows must be separated by a dash.\u00a0 When there are two of the same functional group,\u00a0the name\u00a0must have the prefix \"di\". When there are three of the same functional group, the name must have the prefix \"tri\". When there are four of the same functional group,\u00a0the name\u00a0must have the prefix \"tetra\".\u00a0 However, these prefixes cannot be used when determining the alphabetical priorities.\r\n\r\nThere must always be commas between the\u00a0numbers and the dashes that are between the numbers and the names.\r\n

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    Example<\/h3>\r\nExample 2\r\n\"drawing.gif\"\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \"noname21.gif\"\r\n\r\n(2-b<\/u>romo-1,1-dim<\/u>ethylcyclohexane)\r\n\r\nNotice that \"f\" of fluoro alphabetically precedes the \"m\" of methyl. Although \"di\" alphabetically precedes \"f\", it is not used in determining the\u00a0alphabetical order.\r\n\r\n<\/div>\r\n
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    Example<\/h3>\r\n\"drawing07.gif\"\r\n\r\n(2-fluoro-1,1,-dimethylcyclohexane\u00a0\u00a0\u00a0 NOT<\/strong>\u00a0\u00a0\u00a0 <\/strong>1,1-dimethyl-2-fluorocyclohexane)\r\n\r\n8) If the substituents of the cycloalkane are related by the cis or trans configuration, then indicate\u00a0the configuration\u00a0by placing \"cis-\" or \"trans-\" in front of the name of the structure.\r\n\r\n<\/div>\r\n \r\n\r\n\"3D2.gif\"\r\n\r\nBlue=Carbon\u00a0\u00a0\u00a0 Yellow=Hydrogen\u00a0\u00a0 Green=Chlorine<\/strong>\r\n\r\nNotice that chlorine and the methyl group are both pointed in the same direction on the axis of the molecule; therefore, they\u00a0are cis.\r\n

    \"drawing13.gif\"\u00a0\u00a0\u00a0\u00a0\u00a0cis-1-chloro-2-methylcyclopentane<\/p>\r\n9) After all the functional groups and substituents have been mentioned with their corresponding numbers, the name of the cycloalkane can\u00a0follow.\r\n\r\n<\/div>\r\n

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    Reactivity<\/h3>\r\nCycloalkanes are very similar to the alkanes in reactivity, except for the very small ones, especially cyclopropane. Cyclopropane is\u00a0significantly more reactive than what is expected because of the bond angles in the ring. Normally, when carbon forms four single bonds, the bond angles are approximately 109.5\u00b0. In cyclopropane, the bond angles\u00a0are 60\u00b0.\r\n\r\n\"image\"\r\n\r\nWith the electron pairs this close together, there is a\u00a0significant amount\u00a0of repulsion between the bonding pairs joining the carbon atoms, making the bonds easier to break.\r\n\r\n<\/div>\r\n
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    Alcohol Substituents on Cycloalkanes<\/h3>\r\nAlcohol (-OH) substituents take the highest priority for carbon atom numbering in IUPAC nomenclature. The carbon atom with the alcohol substituent must be labeled as 1. Molecules containing an alcohol group have an ending \"-ol\", indicating the presence of an alcohol group. If there are two alcohol groups, the molecule will have a \"di-\" prefix before \"-ol\" (diol). If there are three alcohol groups, the molecule will have a \"tri-\" prefix before \"-ol\" (triol), etc.\r\n\r\n<\/div>\r\n
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    Example<\/h3>\r\nThe alcohol substituent is given the lowest number even though the two methyl groups are on the same carbon atom and labeling 1 on that carbon atom would give the lowest possible numbers. Numbering the location of the alcohol substituent is unnecessary\u00a0because the ending \"-ol\"\u00a0indicates the presence of\u00a0one alcohol group on carbon atom number 1.\r\n\r\n\"drawing04.gif\"\r\n\r\n2,2-dimethylcyclohexanol\u00a0\u00a0\u00a0\u00a0NOT<\/strong>\u00a0\u00a0\u00a0\u00a01,1-dimethyl-cyclohexane-2-ol\r\n\r\n<\/div>\r\n
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    Example<\/h3>\r\n\"drawing05.gif\"\r\n\r\n3-bromo-2-methylcyclopentanol\u00a0\u00a0\u00a0\u00a0NOT\u00a0\u00a0\u00a0\u00a0<\/strong>1-bromo-2-methyl-cyclopentane-2-ol\r\n\r\n<\/div>\r\n
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    Example<\/h3>\r\n\"noname30<\/strong>\r\n

    Blue=Carbon\u00a0\u00a0\u00a0 Yellow=Hydrogen\u00a0\u00a0\u00a0 Red=Oxygen<\/strong><\/p>\r\n

    \"drawing06.gif\"<\/strong>trans-cyclohexane-1,2-diol<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n

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    Other Substituents on Cycloalkanes<\/h3>\r\nThere are many other functional groups<\/a> like alcohol, which are later covered in an organic chemistry course, and they determine the ending name of a molecule. The naming of these functional groups will be explained in depth later as their chemical properties are explained.\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
    Name<\/strong><\/td>\r\nName ending<\/strong><\/td>\r\n<\/tr>\r\n
    alkene<\/td>\r\n-ene<\/td>\r\n<\/tr>\r\n
    alkyne<\/td>\r\n-yne<\/td>\r\n<\/tr>\r\n
    alcohol<\/td>\r\n-ol<\/td>\r\n<\/tr>\r\n
    ether<\/td>\r\n-ether<\/td>\r\n<\/tr>\r\n
    nitrile<\/td>\r\n-nitrile<\/td>\r\n<\/tr>\r\n
    amine<\/td>\r\n-amine<\/td>\r\n<\/tr>\r\n
    aldehyde<\/td>\r\n-al<\/td>\r\n<\/tr>\r\n
    ketone<\/td>\r\n-one<\/td>\r\n<\/tr>\r\n
    carboxylic acid<\/td>\r\n-oic acid<\/td>\r\n<\/tr>\r\n
    ester<\/td>\r\n-oate<\/td>\r\n<\/tr>\r\n
    amide<\/td>\r\n-amide<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nAlthough alkynes determine the name ending of a molecule, alkyne as a substituent on a cycloalkane is not possible\u00a0because alkynes are planar and would require that the carbon that is part of the ring\u00a0form 5 bonds, giving the carbon atom a negative charge.\r\n\r\n\"pz1.gif\"\r\n\r\nHowever, a cycloalkane with a triple bond-containing substituent is possible\u00a0if the triple bond is not directly attached to the ring.\r\n
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    Example<\/h3>\r\n

    \"pz2.gif\"ethynylcyclooctane<\/p>\r\n\r\n<\/div>\r\n

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    Example<\/h3>\r\n

    \"drawing6.gif\"1-propylcyclohexane\u00a0<\/span><\/p>\r\n\r\n<\/div>\r\n \r\n\r\n<\/div>\r\n

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    Summary<\/h3>\r\n
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    1. Determine the parent chain: the parent chain contains the most carbon atoms.<\/li>\r\n \t
    2. Number the substituents of the chain so that the sum of the numbers is the lowest possible.<\/li>\r\n \t
    3. Name the substituents and place them in alphabetical order.<\/li>\r\n \t
    4. If stereochemistry of the compound is shown, indicate the orientation as part of the nomenclature.<\/li>\r\n \t
    5. Cyclic hydrocarbons have the prefix \"cyclo-\" and have an \"-alkane\" ending unless there is an alcohol substituent present. When an alcohol substituent is present, the molecule has an \"-ol\" ending.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
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      Key Terms<\/h3>\r\n