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课程名称：有机化学 - 一些基本原理和技术 课程概述：本单元学习了有机化合物的结构与反应性的一些基本概念，这些化合物是由于共价键的形成而存在的。有机化合物中共价键的性质可以通过轨道杂化的概念进行描述，其中碳原子可以形成sp³、sp²和sp杂化轨道。不同杂化形式的碳分别对应于甲烷、乙烯和乙炔，并通过该概念可以理解它们的四面体、平面和线性形状。通过杂化轨道的重叠，可以形成不同类型的化学键，如C-H单键（σ键）和C-C键（σ键和π键）。有机化合物可以用各种结构式表示，三维图形可通过楔形和虚线公式绘制。 有机化合物根据其结构或所含功能基团进行分类。功能基团是以独特方式结合在一起的一种原子或原子群，决定了化合物的物理和化学特性。根据国际纯粹与应用化学联合会（IUPAC）制定的规则进行有机化合物的命名，使得名称与结构相对应，读者可以从名称推断出结构。 有机反应机制的概念基于底物分子的结构、共价键的断裂、攻击试剂、电子位移效应及反应条件。这些反应涉及到共价键的断裂与形成。共价键的裂解可分为异裂或同裂，异裂产生碳阳离子或碳阴离子，而同裂则生成自由基作为反应中间体。通过异裂进行的反应涉及互补的反应物对：电子对给体称为亲核试剂，而电子对受体称为亲电试剂。诱导、共振、电迁移和超共轭效应有助于键的极化，使某些碳原子或其他原子的位置成为低或高电子密度点。 有机反应大致可分为取代反应、加成反应、消除反应和重排反应。为了确定有机化合物的结构，进行纯化、定性和定量分析。纯化方法如升华、蒸馏和分馏提取根据一种或多种物理性质的差异进行。色谱法是分离、识别和纯化化合物的有效技术，分为吸附色谱和分配色谱两大类。通过对混合物的组分在吸附剂上的差异吸附，进行分离，而分配色谱则涉及组分在固定相和流动相之间的连续分配。 在得到纯品后，对其进行定性分析以检测所含元素。氮、硫、卤素和磷通过拉萨金测试进行检测；碳和氢的含量通过测量生成的二氧化碳和水量进行估算；氮的含量通过杜马法或凯氏消化法估算，卤素通过卡留斯法进行；硫和磷被氧化为硫酸和磷酸进行估算；氧的百分含量通常通过总百分比（100）与其他所有元素的百分比之和之间的差异来确定。
SUMMARYIn this unit, we have learnt some basic concepts in structure and reactivity of organic compounds, which are formed due to covalent bonding. The nature of the covalent bonding in organic compounds can be described in terms of orbitals hybridisation concept, according to which carbon can have sp3, sp2 and sp hybridised orbitals. The sp3, sp2 and sp hybridised carbons are found in compounds like methane, ethene and ethyne respectively. The tetrahedral shape of methane, planar shape of ethene and linear shape of ethyne can be understood on the basis of this concept. A sp3 hybrid orbital can overlap with 1s orbital of hydrogen to give a carbon - hydrogen (C-H) single bond (sigma, σ bond). Overlap of a sp2 orbital of one carbon with sp2 orbital of another results in the formation of a carbon-carbon σ bond. The unhybridised p orbitals on two adjacent carbons can undergo lateral (side-byside) overlap to give a pi (π) bond. Organic compounds can be represented by various structural formulas. The three dimensional representation of organic compounds on paper can be drawn by wedge and dash formula.Organic compounds can be classified on the basis of their structure or the functional groups they contain. A functional group is an atom or group of atoms bonded together in a unique fashion and which determines the physical and chemical properties of the compounds. The naming of the organic compounds is carried out by following a set of rules laid down by the International Union of Pure and Applied Chemistry (IUPAC). In IUPAC nomenclature, the names are correlated with the structure in such a way that the reader can deduce the structure from the name.Organic reaction mechanism concepts are based on the structure of the substrate molecule, fission of a covalent bond, the attacking reagents, the electron displacement effects and the conditions of the reaction. These organic reactions involve breaking and making of covalent bonds. A covalent bond may be cleaved in heterolytic or homolytic fashion. A heterolytic cleavage yields carbocations or carbanions, while a homolytic cleavage gives free radicals as reactive intermediate. Reactions proceeding through heterolytic cleavage involve the complimentary pairs of reactive species. These are electron pair donor known as nucleophile and an electron pair acceptor known as electrophile. The inductive, resonance, electromeric and hyperconjugation effects may help in the polarisation of a bond making certain carbon atom or other atom positions as places of low or high electron densities.Organic reactions can be broadly classified into following types; substitution, addition, elimination and rearrangement reactions. Purification, qualitative and quantitative analysis of organic compounds are carried out for determining their structures. The methods of purification namely: sublimation, distillation and differential extraction are based on the difference in one or more physical properties. Chromatography is a useful technique of separation, identification and purification of compounds. It is classified into two categories: adsorption and partition chromatography. Adsorption chromatography is based on differential adsorption of various components of a mixture on an adsorbent. Partition chromatography involves continuous partitioning of the components of a mixture between stationary and mobile phases. After getting the compound in a pure form, its qualitative analysis is carried out for detection of elements present in it. Nitrogen, sulphur, halogens and phosphorus are detected by Lassaigne's test. Carbon and hydrogen are estimated by determining the amounts of carbon dioxide and water produced. Nitrogen is estimated by Dumas or Kjeldahl's method and halogens by Carius method. Sulphur and phosphorus are estimated by oxidising them to sulphuric and phosphoric acids respectively. The percentage of oxygen is usually determined by difference between the total percentage (100) and the sum of percentages of all other elements present.
