Question

Draw the most stable conformation for; a. trans-1-chloro-3-methylcyclohexane b. cis-1-ethyl-2-isopropylcyclohexane c. trans-1-bromo-4-ethylcyclohexane d. cis-2-bromo-1-methylcycclohexane Sppecifically, show the ring flipping and calculate the strain using the table given in the power point slides.

Answer 1

Solution: In case of cyclohexane, it exists mainly in 3D chair conformation instead of planar hexagonal structure to reduce torsional strain. At room temperature, it can flip to another chair conformation via several conformation intermediates such as half-chair, twist boat and boat. In this flipping process, the axial and equatorial bonds change their conformation as well. This process is shown below, If two groups are present in the same direction from the cyclohexane ring, it will call a 'cis' conformation and if they are opposite in direction, they are called 'trans' conformation. Now, if we draw the most stable conformations along with their flipping, it will look like for each individual molecule as follows a. trans-1-chloro-3-methylcyclohexane Сн, н

b. cis-1-ethyl-2-isopropylcyclohexane H5_2 H3CCH3 TH 모 C2H5 모 c. trans-1-bromo-4-ethylcyclohexane Br н,с d. cis-2-bromo-1-methylcyclohexane H2C H The strain values can not be calculated as table is not attached with the question.