{'fraction_non_alphanumeric': 0.0220125786163522, 'fraction_numerical': 0.006289308176100629, 'mean_word_length': 5.066666666666666, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Pressure Effect on Hydrogen Bonding in Aqueous Diets-Alder Reactions

The kinetic pressure effect on Diels-Alder reactions involving methyl vinyl ketone and conjugated dienes is investigated in organic and water solution with and without a H-bond generator (paranitrophenol) respectively. Whereas the difference in activation volumes is zero in organic solution, it amounts 3 - 4 cm3. mol-1 in water. Such result points to an increased polarization of the keto group in aqueous solution ascribed to enhanced hydrogen bonding. It is suggested that hydrogen bond effects contributes to the kinetic effect in aqueous Diels-Alder reactions.