Acidity of dibasic carbon acids. Part 5.1–4 The second acidity constant of 9,10-dihydrodibenz[a,h]anthracene in tetrahydrofuran—geometry, charge distribution of dianion, structure of dimetallic salts
作者:Malka Nir、Israel O. Shapiro、Mordecai Rabinovitz
DOI:10.1039/a604331c
日期:——
The second equilibrium ion pair acidity constant
(pK2) of
9,10-dihydrodibenz[a,h]anthracene (DBDHA,
1H2) with counter ions sodium (pK2 28.5)
and potassium (pK2 30.4) has been determined in
tetrahydrofuran (THF) at 298 K. This value is considerably lower than
for other 9,10-dihydroanthracene derivatives. Disodium, dipotassium and
dirubidium salts of DBDHA, i.e. 12-, exist as
contact ion triplets in THF at 298 K, although the dilithium salt
behaves as a solvent-separated ion triplet under the same conditions. In
the dianion of DBDHA (12-) the negative charge is
displaced from the deprotonated carbon atoms towards the outer benzene
rings.
9,10-二氢二苯[a,h]蒽(DBDHA,1H2)在298 K下与钠(pK2 28.5)和钾(pK2 30.4)对离子在四氢呋喃(THF)中的第二平衡离子对酸度常数(pK2)已经确定。这个值明显低于其他9,10-二氢蒽衍生物。DBDHA的二钠、二钾和二铷盐,即12-,在298 K的THF中作为接触离子三重体存在,尽管二锂盐在相同条件下表现为溶剂分离离子三重体。在DBDHA的二负离子(12-)中,负电荷从去质子化的碳原子向外部苯环偏移。