Preparation of 1-Aryl-2-bromo-3,3-difluorocyclopropenes

Abstract

Aryl-2-bromo-3,3-difluorocyclopropanes were prepared from the reaction of 2',2'-difluorostyrene and dibromocarbene instead of from 1-aryl-2-haloacetylenes and difluorocarbene. These results are rationalised by the energy gap between HOMO (styrene) , HOMO (acetylene) and LUMO (CX2) . The title compounds were converted to methyl arylpropynoate in MeOH solution in quantitative yield.

A baroclinic instability test case for atmospheric model dynamical cores

“…The baroclinic-wave test sequence has been applied to the three hydrostatic dynamical cores that are part of National Center for Atmospheric Research's Community Atmosphere Model version 3 (NCAR CAM3). In particular, these are a finite-volume dynamical core (Lin 2004) and the spectral transform semi-Lagrangian and Eulerian dynamics packages. They are documented in Collins et al (2004) who also discuss the exact equation sets.…”

“…The mass-conservative finite-volume (FV) dynamical core in flux form is built upon a 2D shallow-water approach in the horizontal plane (Lin andRood 1996, 1997). The vertical discretization utilizes a 'Lagrangian control-volume' principle, which is based on a terrain-following 'floating' Lagrangian coordinate system and a fixed 'Eulerian' reference frame.…”

“…The vertical discretization utilizes a 'Lagrangian control-volume' principle, which is based on a terrain-following 'floating' Lagrangian coordinate system and a fixed 'Eulerian' reference frame. In particular, the vertically stacked finite volumes are allowed to float for a duration of several time steps before they are mapped back monotonically and conservatively to the fixed reference system (Lin 2004). The latter coincides with the hybrid levels of CAM3's Eulerian and semi-Lagrangian dynamical cores.…”

“…Indeed, for some schemes, such as those incorporating nonlinear shape preservation, the inherent diffusion can not be isolated. Thus this test allows the comparison of schemes with very different diffusive behaviours, like a spectral transform semi-Lagrangian method (Collins et al 2004) or a monotonic finite volume technique (Lin 2004), that do not require explicit horizontal diffusion to control the solution spectra at the small scales. In contrast, alternative schemes, like a spectral transform Eulerian method (Collins et al 2004) or a finite-difference approach on an icosahedral grid (Majewski et al 2002), generally apply a rather scale-selective fourth-order horizontal diffusion mechanism to prevent the accumulation of kinetic energy in the smallest scales or to ensure numerical stability.…”

The LMARS Based Shallow‐Water Dynamical Core on Generic Gnomonic Cubed‐Sphere Geometry

“…Therefore, geophysical fluid models usually discretize the governing equations with various grid staggering choices (Arakawa & Lamb, 1977, namely A-, B-, C-, D-Grid) to gain numerical advantages in resolving the smallest waves. In particular, the C-Grid results in natural pressure gradient in the momentum equations and straightforward divergence representation (Adcroft et al, 2019); the D-Grid forms a perfect vorticity mode (Lin, 2004;Harris & Lin, 2013), which dominants large-scale to mesoscale atmospheric motions. With the recent rapid increase of computational power, the GCM community is pushing the model resolution aggressively to about a globally-kilometer horizontal scale (Stevens et al, 2019;Satoh et al, 2019).…”