Benzene ring, hydrogenation

The NMR spectrum of the cyclophane shows three signals at 6 4.27, 6.97, and 7.24 (1 2 1 ratio) due to the benzene ring hydrogens. Examine cyclophane and identify which hydrogens are responsible for each signal. 

The hydrogenation of aryl aldehydes and ketones is complicated by the potential for the hydrogenolysis of the resulting benzyl alcohol as well as benzene ring hydrogenation (Eqn. 18.3). With the proper selection of reaction conditions... 

Alkyl phenols as mentioned earlier are phenol derivatives wherein one or more of the benzene ring hydrogens are substituted by an alkyl group. Cresols are monosubstituted methyl phenols, xylenols are dialkyl phenols with two methyl groups. Similarly other alkyl groups such as butyl phenols, butyl cresols are also examples of alkyl phenols. Some of them... 

Aromatic compounds have two characteristic types of hydrogens aromatic ring hydrogens (benzene ring hydrogens) and benzylic hydrogens (those attached to an adjacent carbon atom). 

Hydrogenation of a benzene ring. Hydrogenation of (R)-a-phenylglycine with Pd/C in aqueous alkaline solution results in formation of phenylacetic acid, but use of Pd(OH)a/C leads to (R)-a-cyclohexylglycine (40-60% yield 84% ee) and cyclohexylacetic acid (35-55%, yield). ... 

Rhodium-alumina Benzene ring hydrogenation with formation of sec. alcohols from ketones... 

Sec. alcohols from ketones with benzene ring hydrogenation... 

An alkene (vinylic) hydrogen can be distinguished from a benzene ring hydrogen via H-NMR spectroscopy. (11.10)... 

Platinum oxide/acetic acid Selective benzene ring hydrogenation with retention of benzylic oxygen... 

Redox properties metal increases the formation of benzene ring hydrogenation and creates more vacancies. 

---