附件2 粒大浮 教 案 2003~~2004学年第Ⅰ学期 院(系、所、部)化学与环境学院有机化学研究所 教研室有机化学 课程名称有机化学(双语教学 授课对象化学教育 授课教师杨定乔 职称职务教授 教材名称 Organic Chemistry 2003年09月01日
附件 2 教 案 2003~~ 2004 学年 第 I 学期 院（系、所、部）化学与环境学院有机化学研究所 教 研 室 有机化学 课 程 名 称 有机化学(双语教学) 授 课 对 象 化学教育 授 课 教 师 杨定乔 职 称 职 务 教授 教 材 名 称 Organic Chemistry 2003 年 09 月 01 日
有机化学(双语教学)课程教案 授课题目(教学章节或主题):第五章.脂环烃授课类型理论课 Cycloalkanes 第6周第17-22 授课时间 教学目标或要求∶了解脂环烃的结构,分类和命名以及脂环烃的化学性质。掌握环己 烷的构象。 教学内容(包括基本内容、重点、难点) Cycloalkane Nomenclature The ability of carbon to form bonds with itself allows for the possibility of the formation of cyclic compounds. In nature, cyclic compounds with ring sizes from 3 to 30 carbons are known; five- and six-member rings are especially common For a simple cycloalkane the general molecular formula is CHa, where n is the total number of carbons. You will note that this differs from the general formula for an alkane(C, H)by the lack of the two additional hydrogens(the"+2 term") As a general rule, every ring which is constructed from an alkane reduces the number of hydrogens in the molecular formula for the parent hydrocarbon by 2. Thus one ring gives CHa, two rings within the molecule would give a molecular formula of the type CHasn, three rings, CH, etc. Thus by simply examining the molecular formula of an alkane or cycloalkane, you can immediately calculate the number of rings within the molecule. Th ion can be expanded to also include double bonds (which also reduce the number of hydrogens in an alkane by two) to give the concept of degree of unsaturation, which is covered in a later section. Using this simple calculation, the total number of rings and multiple bonds in a molecule can be calculated, based simply on the observed molecular formula. Molecular models of cycloalkanes with n=3 to 7 are shown below. You should note that, in the smaller ring sizes (3, 4 and 5), the bond angles are significantly less than the optimal 109. 5 This results in a significant amount of ring strain in these compounds which make many small rings susceptible to ring-opening reactions. The bond angles in a six-membered ring match well with the tetrahedral geometry of carbon and there is virtually no ring strain in these compounds. Rings which are seven-membered and larger are
有机化学(双语教学) 课程教案 授课题目（教学章节或主题）：第五章．脂环烃 (Cycloalkanes) 授课类型 理论课 授课时间 第 6 周第 17-22 节 教学目标或要求：了解脂环烃的结构，分类和命名以及脂环烃的化学性质。掌握环己 烷的构象。 教学内容（包括基本内容、重点、难点）： Cycloalkane Nomenclature The ability of carbon to form bonds with itself allows for the possibility of the formation of cyclic compounds. In nature, cyclic compounds with ring sizes from 3 to 30 carbons are known; five- and six-member rings are especially common. For a simple cycloalkane the general molecular formula is CnH2 n, where n is the total number of carbons. You will note that this differs from the general formula for an alkane (CnH2n+2) by the lack of the two additional hydrogens (the "+ 2 term"). As a general rule, every ring which is constructed from an alkane reduces the number of hydrogens in the molecular formula for the parent hydrocarbon by 2. Thus one ring gives CnH2 n, two rings within the molecule would give a molecular formula of the type CnH2 n-2, three rings, CnH2 n-4, etc. Thus by simply examining the molecular formula of an alkane or cycloalkane, you can immediately calculate the number of rings within the molecule. This notion can be expanded to also include double bonds (which also reduce the number of hydrogens in an alkane by two) to give the concept of degree of unsaturation, which is covered in a later section. Using this simple calculation, the total number of rings and multiple bonds in a molecule can be calculated, based simply on the observed molecular formula. Molecular models of cycloalkanes with n = 3 to 7 are shown below. You should note that, in the smaller ring sizes (3, 4 and 5), the bond angles are significantly less than the optimal 109.5o. This results in a significant amount of ring strain in these compounds which make many small rings susceptible to ring-opening reactions. The bond angles in a six-membered ring match well with the tetrahedral geometry of carbon and there is virtually no ring strain in these compounds. Rings which are seven-membered and larger are
highly distorted, and again display significant ring strain. The nomenclature for a simple cycloalkane is based on the parent hydrocarbon with the simple addition of the prefix cyclo. a three-membered ring is therefore cyclopropane, four-membered, cyclobutane, five-membered, cyclopentane, six-membered, cyclohexane, etc. HH H alkane five carbons As a convenient shortcut, cyclic structures are usually drawn using line (structural or line-angle) drawings, as shown above. Again, it is important to understand that every vertex in these drawings represents a-CH: group, every truncated line a -CH, group and intersections of three or four lines represent 3 or 4 carbons, respectively. Substituents on cycloalkanes are named using the conventions described for alkanes, with the exception that, on rings bearing only one substituent, no number is needed; otherwise numbering proceeds to produce the lowest number at the first point of difference
highly distorted, and again display significant ring strain. The nomenclature for a simple cycloalkane is based on the parent hydrocarbon, with the simple addition of the prefix cyclo. A three-membered ring is therefore cyclopropane, four-membered, cyclobutane, five-membered, cyclopentane, six-membered, cyclohexane, etc. As a convenient shortcut, cyclic structures are usually drawn using line (structural or line-angle) drawings, as shown above. Again, it is important to understand that every vertex in these drawings represents a -CH2- group, every truncated line a -CH3 group and intersections of three or four lines represent 3 o or 4o carbons, respectively. Substituents on cycloalkanes are named using the conventions described for alkanes, with the exception that, on rings bearing only one substituent, no number is needed; otherwise numbering proceeds to produce the lowest number at the first point of difference
.CHs H3 methylcyclopropane 1.2-dimethylcyclopentane 1, 1-dimethylcyclohexane CH3 CH3CH2 l-ethy l-4-methy cyc lohe imethy cyclohexane (assign numbers to give lowest number at first point of difference; arrange alphabetically) CH3 1-ethy 1-1 me thy cycloheptane 1-cyclopropy 1-1-methy cyclohexane Polycyclic carbons, such as those shown below, are common in organic chemistr Carbons in these compounds which are shared between attached rings are termed bridgehead carbons, and, in the special case where only one carbon is shared between rings, the bridging carbon is referred to as a spiro carbon. Polycyclic compounds are named and numbered using a complex system to indicate ring sizes and attachments, and will be covered later. Conformations of Alkanes Cycloalkanes Structural formulas are useful for showing the attachment of atoms, and three-dimensional drawings are useful for showing molecular shapes. Neither of these, however, conveys much information regarding the dynamics of molecular conformations and the role that these play in controlling equilibrium shapes and reactivity of organic molecules. ed previously, there is generally free rotation around carbon-carbon ingle bonds. At room temperature, this rotation can be quite rapid and can occur with a rate constant of *10 sec. For ethane, this rotation has only a small intrinsic energy barrier since the van der Waals radius of the hydrogen atoms on the adjacent carbons is sufficiently small so that overlap is minimal
Polycyclic carbons, such as those shown below, are common in organic chemistry. Carbons in these compounds which are shared between attached rings are termed bridgehead carbons, and, in the special case where only one carbon is shared between rings, the bridging carbon is referred to as a spiro carbon. Polycyclic compounds are named and numbered using a complex system to indicate ring sizes and attachments, and will be covered later. Conformations of Alkanes & Cycloalkanes Structural formulas are useful for showing the attachment of atoms, and three-dimensional drawings are useful for showing molecular shapes. Neither of these, however, conveys much information regarding the dynamics of molecular conformations and the role that these play in controlling equilibrium shapes and reactivity of organic molecules. As mentioned previously, there is generally free rotation around carbon-carbon single bonds. At room temperature, this rotation can be quite rapid and can occur with a rate constant of 108 sec-1. For ethane, this rotation has only a small intrinsic energy barrier since the van der Waals radius of the hydrogen atoms on the adjacent carbons is sufficiently small so that overlap is minimal
A movie file demonstrating this rotation is shown below (Click on the icon above to view the movie, use the BACK button to return to this page This can be contrasted, however with rotation around the central carbon-carbon bond in butane, shown in the movie panel below, in which two me l gro clearly overlap during a single rotation(the van der Waals radii of the methyl hydrogen atoms clearly overlap) s3 keal/m The rotation around the single bond in ethane, while not obviously hindered, does generate conformational isomers having different potential energies. As shown above, as the dihedral angle between the ethane hydrogen atoms changes from 60(a staggered conformation) to 120(an eclipsed conformation),the potential energy of the molecule increases by about 3 kcal/mole. As the me l group continues to rotate towards 180, the potential energy again drops and rises again as the next eclipsed structure is formed
A movie file demonstrating this rotation is shown below: (Click on the icon above to view the movie; use the BACK button to return to this page) This can be contrasted, however, with rotation around the central carbon-carbon bond in butane, shown in the movie panel below, in which two methyl groups clearly overlap during a single rotation (the van der Waals radii of the methyl hydrogen atoms clearly overlap). The rotation around the single bond in ethane, while not obviously hindered, does generate conformational isomers having different potential energies. As shown above, as the dihedral angle between the ethane hydrogen atoms changes from 60 (a staggered conformation) to 120 (an eclipsed conformation), the potential energy of the molecule increases by about 3 kcal/mole. As the methyl group continues to rotate towards 180 , the potential energy again drops and rises again as the next eclipsed structure is formed