有机化学（英文讲义）Chapter 2.pptVIP

Chapter 2 Organic Compounds - A First Look 2.1~2.3 Brief introduction of hydrocarbons Hydrocarbons – alkanes, alkenes, alkynes and arenes 1. alkane (C-C single bond, saturated compound): e.g. C2H6: 2. alkene (olefin, C=C double bond, unsaturated compound): C2H4: internal olefins (CH3CH=CHCH3) linear olefins terminal olefins (CH2=CHCH2CH3) chain alkenes branched olefins (internal and terminal) 3. alkyne (C≡C bond, unsaturated compound): internal alkynes (H3CC≡CCH3) terminal alkynes (CH3CH2C≡CH) 4. arene—aromatic hydrocarbons, e.g. benzene (苯), naphthalene (萘), anthracene (蒽), phenanthrene (菲) … Bond length and bond energy of hydrocarbons Bond length: the distance between the nuclei of two bonded atoms. Bond dissociation energy (D): the amount of energy required for homolysis of a covalent bond. Bond energy ( ): the average value of bond dissociation energy. For binuclear molecules: H2, Cl2 D = For multinuclear molecules: (CH4) = (D1+D2+D3+D4)/4 bond length: C-H bond energy ( ): C(sp3)-H C(sp2)-H C(sp)-H 2.5 Degree of unsaturation (The index of hydrogen deficiency) degree of unsaturation (DU, the total number of multiple bonds and rings) DU = C6H8: If DU = the consumed molar amount of H2, no ring exists in the molecule. If DU the consumed molar amount of H2, there are n rings in the molecule. n = DU – the actually consumed molar amount of H2 2.6, 2.7, 4.7 Physical properties and molecular structures ◆ Forces that act among molecules and ions i. ion-ion force ii. dipole-dipole force iii. London force (instantaneous dipole, induced dipole