Unavoidable crowding

The carbonyl C of RCOOH and RCOOR is trigonal sp -hybridized, but that of the intermediate is tetrahedral sp -hybridized. If R in R OH or R in RCOOH is extensively branched, formation of the unavoidably crowded transition state has to occur with greater difficulty and more slowly. 

A cause unavoidable crowding leading to steric hindrances between nitro groups, which prevents their rotations freely since there is no space. The phenylene fragment is close to planarity while the five-membered ring is planar [189]. 

This question of what biomolecules da to water in the cell is unavoidable, since there is probably rather little water that does not feel their presence. The cell is a crowded place (Fig. 6.3). Macromolecules typically occupy 5 0% of the total volume [15], so that on average they are typically separated by only 1-2 nm. This crowding may have a strong impact on the dynamics and interactions between... 

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