Question

K _ [equatorial] 3) Provide an explanation for the results shown below involving monosubstituted cyclohexanes at 25°C. (6 points) Substituent ſaxial] -H -CH3 18 -CH2CH3 21 -CH(CH3)2 35 -C(CH3)3 4800

Answer 1

In case of study of the chair form of The g monasubstituted Cyclohenans, we see that equitorial substituted in more stable than the ancial substituent. Because À sterically ulky go in an anial position interacts with the two hydrogen atoms, also anial in relative C-3 C-5 position, and the conformation eruilibrium is dis placed towards the equitorial conformation. This type of interaction b called 1,3 dianial interaction. , ... ----R any inversion 2 Jing inversion Arial H conformation Equatorial Conformation Rz substituent.. When The the steric size of depusion the also increase substituent increase. In this court case me # => R2iH R= -Clig me 13 me 13 R2 - CH2CH3 Haun me X 4-3-metime Me 1 R2 - CHA CH-CH

As the size of the substituent increases the steric replusion also increase in the axial position .But in equation confirmation there was no such interaction .

In case 1> the hydrogen in the axial and equatoral no change in the substituent therefore the equitorial and the axial population is same.

Case 2> The size of the - CH_{​​​​​3}​​​​ is larger than hydroden and it has the C-H bond.Then there is a 1,3 diaxial interaction with the C-H bond of CH_{​​​​​3 .}Therefore equilibrium concentration of the axial is less than equitorial.

Case3>Here the size of the substituent,CH₂CH₃is greater than CH_​3.​​​CH3.So the axial steric repulsion also increases.To minimize the repulsion it rotate it self.

The - @ehut дером minimize greater zotation of substituent to minimize the depulsion depusion

Case 4> Here size of the substituent is greater than that before.And also Here One C-H bond in CH(CH_{​​​​​3}​​​​).So there was a chance of rotation to minimize the repulsion .

Case 5>There observed that there was k_{​​​​​​eq} value is unexpectedly very high .This is because there was no C-H bond in this substituent So there was no chance of rotation to minimize the repulsion.The syn axial interacton with the CH_{​​​​​3}

group of C(CH)₃ with the 3-H ,5-H so high that it prefers to stay in the equitorial position.

So we see this type of observation.