2-(3-Hydroxy-propyl)isoindoline-1,3-dione:Competition among hydrogen-bond acceptors

The title compound, C11H11NO3, has two mol-ecules in the asymmetric unit, which differ in the orientation of their side-chain OH groups, allowing them to form inter-molecular O - H⋯O hydrogen bonds to different acceptors. In one case, the acceptor is the OH group of the other mol-ecule, and in the other case it is an imide O=C group. This is the first example in the N-substituted phthalimide series in which independent mol-ecules have different types of acceptor. Mol-ecular-orbital calculations place the greatest negative charge on the OH group. © 2008 International Union of Crystallography

Structure and properties of (hydroxy)alkylammonium salts of flurbiprofen

Interactions with hydrogen atoms strongly affect the structure of salts of the anti-inflammatory drug flurbiprofen. With cations of the form H3N+C(CH3)3-n(CH2OH)n for n = 0-3 charge-assisted hydrogen bonding is the most obvious feature. In the t-butylammonium (n = 0) salt successive R43(10) rings are formed by +N-H…OCO- interactions. With n = 1 the additional OH is disordered and has little effect. However, n = 2 changes the pattern: now one +N-H…OCO- and one O-H…OCO- hydrogen bond link a cation to a carboxylate anion. When n = 3, this motif persists in one polymorph. However, another polymorph has two independent anions related by pseudo-translation and two independent cations related by a pseudo-glide, while extensive disorder results from application of the “opposite” pseudo-symmetry operation. Enantiomer discrimination at flurbiprofen sites depends on the environment of H and CH3 in the HCCH3 group. Hirshfeld surfaces show normal van der Waals contacts around ordered methyl groups but tight contacts around major sites for disordered ones, which become worse around the minor sites. Similar effects are observed in the vicinity of the fluorine atoms in the fluorophenyl rings. Whereas the major sites for disordered atoms and the sites for ordered atoms are involved in normal or slightly short van der Waals contacts, the minor sites suffer from tighter contacts. 2

A review of measurement and modelling results of particle atmosphere–surface exchange

Atmosphere–surface exchange represents one mechanism by which atmospheric particle mass and number size distributions are modified. Deposition velocities (vd) exhibit a pronounced dependence on surface type, due in part to turbulence structure (as manifest in friction velocity), with minima of approximately 0.01 and 0.2 cm s−1 over grasslands and 0.1–1 cm s−1 over forests. However, as noted over 20 yr ago, observations over forests generally do not support the pronounced minimum of deposition velocity (vd) for particle diameters of 0.1–2 μm as manifest in theoretical predictions. Closer agreement between models and observations is found over less-rough surfaces though those data also imply substantially higher surface collection efficiencies than were originally proposed and are manifest in current models. We review theorized dependencies for particle fluxes, describe and critique model approaches and innovations in experimental approaches, and synthesize common conclusions of experimental and modelling studies. We end by proposing a number of research avenues that should be pursued in to facilitate further insights and development of improved numerical models of atmospheric particles