There are two stereoisomers of 1-tert-butyl-4-chloro-cyclohexane. One of these isomers reacts with sodium ethoxide in an E2 reaction that is 500 times faster than the reaction of the other isomer. Identify the isomer that reacts faster, and explain the difference in rate for these two isomers.

Explanation:

cis-isomer reacts faster

Explanation:

The missing diagrams in the question are attached in the first image below and the isomers that react faster are shown in the second image attached.

The cis-isomer quickly follows E2 reaction due to the fact that it is locked in a chair conformation whereby chlorine dominates an axial position, as displayed in drawing C as well as the leaving group Cl which is antiperiplanar to a beta proton.

Due to the bulkiness of tert-butyl, the trans-isomer is Basically trapped in a chair configuration, with chlorine occupying an equatorial position as displayed in drawing A below, thus leaving the group isn't antiperiplanar to a beta proton.

Tert butyl favors an equatorial position due to its bulkiness. This makes the Cl to assume an axial position in an isomer

The difference:

From the second image attached below, in the first diagram(1):

Suppose H is antiperiplanar, C-H bond electrons reach antibonding orbitals of C-Cl, assisting in the breakdown of the C-Cl bond and therefore speeding up the process.

From the second diagram(2) in the second image:

Unless Cl is in the axial position would it have β-hydrogen in the antiperiplanar position. Because tert-butyl prefers equatorial location, the Cl occupies equatorial position in the trans isomer.

As a result, the reaction is slower and there is no β-hydrogen antiperiplanar to Cl.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.