定义Definition
锯架投影式从斜上方观察 C–C 键：中心键斜画，前碳在左下、后碳在右上，各自的三个取代基呈“Y”形画出，可同时看出构象与原子连接。
A sawhorse projection views a C–C bond obliquely: the central bond is drawn diagonally with the front carbon lower left and rear carbon upper right, each with its three substituents in a ‘Y’, showing conformation and connectivity together.
特点Features
比纽曼式更直观地显示分子立体形状，但二面角不如纽曼式清晰。常用于表示乙烷、丁烷的交叉式与重叠式，以及从纽曼式到楔形式的转换。
More pictorial than a Newman projection but less clear about dihedral angles; used for staggered and eclipsed ethane and butane and as a bridge between Newman and wedge drawings.
转换Interconversion
把锯架式沿中心键轴“看进去”即得纽曼式；把前碳放在纸面、后碳在纸后即得楔线–虚线式。
Looking down the central bond gives the Newman projection; placing the front carbon in the plane and the rear one behind gives the wedge–dash form.
应用Application
分析邻二卤代烷的 E2 消除、溴对烯烃的反式加成立体化学时常用。
Handy for analysing E2 eliminations of vicinal dihalides and the stereochemistry of anti Br₂ additions.
年表Timeline
- 1950s
与纽曼式一同在构象分析中普及
Popularised with Newman projections in conformational analysis