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(i) Saw horse representation: In this projection, the molecule is viewed along the axis of the model from an oblique angle. The central carbon-carbon bond (C-C) is draw as a straight line slightly tilted to right for the sake of clarity. The front carbon is shown as the lower left hand carbon and the rear carbon is shown as the upper right hand carbon. The three bonds around each carbon atom ( C- H in ethane orC-C  in higher alkanes) are shown by three lines.

 

 

(ii) Newman projection : This is a simple method to represent the conformations. In this method, the molecule is viewed from the front along the carbon-carbon bond axis. The two carbon atoms forming the?-bond are represented by two circles; one behind the other so that only the front carbon is seen. The front carbon atom is shown by a point whereas the carbon further from the eye is represented by the circle. Therefore, the C - H bonds of the front carbon are depicted from the centre of the circle while C- H bonds of the back carbon are drawn from the circumference of the circle at an angle of 120° to each other.