Part 5a. Rotamers. Answers the following questions about the C-C bond indicated below 3-methylhexane H/H eclipsed CH3/H eclipsed CH3CH₂/H eclipsed CH3/CH3 eclipsed CH3/CH₂CH3 eclipsed CH₂CH3/CH₂CH3 eclipsed CH3/CH3 gauche CH3CH₂CH3 gauche CH₂CH3/CH₂CH3 gauche 1.0 kcal/mol 1.5 kcal/mol 1.6 kcal/mol 2.5 kcal/mol 3.0 kcal/mol 5.1 kcal/mol 0.9 kcal/mol unknown 1.6 kcal/mol (a) Draw the most stable rotamer, using a newman projection, for the C3-C4 bond of 3- methylhexane. (b) Draw the least stable rotamer, using a newman projection, for the C3-C4 bond of 3-methyl hexane. (c) The barrier to rotation for the C3-C4 bond of 3-methylhexane is 6.3 kcal/mol. Given this information, and the information provided above, what is the energy cost for a CH3CH₂C gauche interaction? (show your work)
Reactive Intermediates
In chemistry, reactive intermediates are termed as short-lived, highly reactive atoms with high energy. They rapidly transform into stable particles during a chemical reaction. In specific cases, by means of matrix isolation and at low-temperature reactive intermediates can be isolated.
Hydride Shift
A hydride shift is a rearrangement of a hydrogen atom in a carbocation that occurs to make the molecule more stable. In organic chemistry, rearrangement of the carbocation is very easily seen. This rearrangement can be because of the movement of a carbocation to attain stability in the compound. Such structural reorganization movement is called a shift within molecules. After the shifting of carbocation over the different carbon then they form structural isomers of the previous existing molecule.
Vinylic Carbocation
A carbocation where the positive charge is on the alkene carbon is known as the vinyl carbocation or vinyl cation. The empirical formula for vinyl cation is C2H3+. In the vinyl carbocation, the positive charge is on the carbon atom with the double bond therefore it is sp hybridized. It is known to be a part of various reactions, for example, electrophilic addition of alkynes and solvolysis as well. It plays the role of a reactive intermediate in these reactions.
Cycloheptatrienyl Cation
It is an aromatic carbocation having a general formula, [C7 H7]+. It is also known as the aromatic tropylium ion. Its name is derived from the molecule tropine, which is a seven membered carbon atom ring. Cycloheptatriene or tropylidene was first synthesized from tropine.
Stability of Vinyl Carbocation
Carbocations are positively charged carbon atoms. It is also known as a carbonium ion.
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