[理学]7炔烃二烯烃.ppt

Carrots, Alkenes, and the Chemistry of Vision 1 5 11 12 15 Folk medicine has long held that eating carrots is good for your eyes. Although that’s probably not true for healthy adults on aproper diet. there’s no question that the chenmistry of carrots and the chenmistry of vision are related. Carrots are rich in β- carotene, a purple-orange alkene that is an excellent dietary source of vitamin A. β- carotene is converted to vitamin A by enzymes in the liver, oxidized to an aldehyde called all-trans-retional, and then isomerized by a change in geometry of the C11-C12 doubie bond to produced 11-cis- retinal, the light-sensitive pigment on which the visual systems of all living things are basd on. There are two types of light-sensitive receptor cells in the retina of the human eye, rod cells and cone cells. The three milliion or so rod cells are primarily responsible for seeing in dimlight, whereas the hundred million cone cells are responsible for seeing in bright light and for the percep- tion of bright colors. In the rod cells of the eye, 11-cis-retinal is converted into rhodopsin, a light-sensitive substance formed from the protein opsin and 11- cis- retinal. When light strikes the rod cells, isomerization of C11-C12 double bond occurs and trans-rhodopsin, called metarhodopsin II , is produced. This cis-trans isomerization of rhodopsin is accompanied by a change in molecular geometry, which in Turn causes a nerver impulse to be sent to the brain where it is perceived as vision.(In the absence of light, the cis-trans isomerization takes approximately 1100 years; in the presence of light, it occurs 2×10 -11 seconds!) Metarhodopsin II is than recycled back into rhodopsin by a multistep sequence involving cleavage to all-trans-retinal and cis-trans isomerization back to 11-cis –retinal. §7 炔烃和二烯烃 基本要求 1 炔烃的性质（烯炔的加氢、加卤、库切列洛夫反应、部分氢化） 2 烯炔的命名；炔烃的制备； 3共轭二烯的特性反应（Diels-Alder反应，1,4- 1,2-加成）； 4共振式的写法； 5丙二烯，共轭二烯的结构。 §7.1 炔烃的结构、命名和物理性质 1 炔烃的结构 事实 解释：SP杂化 SP杂化轨道 乙炔分