Solution: n-Hexanol (MOb 02) is a primary alcohol, whose carbon chain has no branches. Therefore, the strategy is reduced to looking for reactions that allow the chain to grow in a good number of carbon atoms. It is not advisable that the growth of the chain is one by one, since this path would lead to a synthesis plan with many stages, consequently a low yield.
As such, the opening of epoxide rings by a Grignard compound can be adequate for this purpose; as it can also be combined with acetylenic synthesis (use of derivatives of sodium acetylide and subsequent saturation of the triple bond).
The epoxide needed to combine with the Grignard is prepared from an alkene and a peracid acid. Thus, the present synthesis plan is deduced, where the starting materials can be acetylene and the ethanol.
Synthesis of 7-methyl-3-pentene (MOb 03)
Solution:This molecule is a nonsymmetrical alkene. The best option to generate a precursor molecule of this type is to resort to acetylenic synthesis, that is to say, consider the alkene as a product of a partial hydrogenation of the alkyne triple bond, for which the best option is the use of the Lindlar catalyst.
Subsequently, the respective alkyl halides are reacted with the sodium acetylides that are formed with the sodamide.
Once again, we find an alcohol as an intermediate precursor molecule, which needs to be prepared by opening an epoxide. The starting materials are acetylene and acetaldehyde.
