Formaldehyde dimer

K.E. Riley, K.M. Merz Jr., Insights into the strengths and origins of halogen bonding The halobenzene-formaldehyde dimer. J. Phys. Chem. A 111, 1688-1694 (2007)... 

Xantheas and co-workers [159,160] have incorporated polarization in a model scheme and have used that to provide a clear basis for the enhancement of water s dipole in ice. A model potential with polarization has been reported for the formaldehyde dimer [161]. It is an example of a carefully crafted potential, which is system-specific because of its application to pure liquid formaldehyde, but which has terms associated with properties and interaction elements as in the above models. As well, some of the earliest rigid-body DQMC work, which was by Sandler et al. [162] on the nitrogen-water cluster, used a potential expressed in terms of interaction elements derived from ab initio calculations with adjustment (morphing). Stone and co-workers have developed interaction potentials for HF clusters [163], water [164], and the CO dimer [165], which involve monomer electrical properties and terms derived from intermolecular perturbation theory treatment. SAPT has been used for constructing potentials that have enabled simulations of molecules in supercritical carbon dioxide [166]. There are, therefore, quite a number of models being put forth wherein electrical analysis and/or properties of the constituents play an essential role, and some where electrical analysis is used to understand property changes as well as the interaction energetics. 

Figure 20 Second derivative of the energy with respect to the coordinate of the two oxygens in formaldehyde dimer, The two monomers lie in the xy plane in the orientation shown in Figure 19. The abscissa is the distance between the two oxygens. OPTS, ref. 65 HL, ref. 116 LFfD, ref. 106. The dispersion term was omitted from the curves based on these references. Note that an r" repulsion term fits the ab initio data much better than the form. (Reprinted with permission from ref. 70, copyright 1989 American Chemical Society.)...

The Prins reaction has been modelled using DFT (density functional theory), using an alkene (RCH=CH2, R = Me or Ph), a formaldehyde dimer, and a proton-water cluster, H30" (H20)i3. Both alkenes feature a concerted path to give the 1,3-diols. An unprecedented hemiacetal intermediate, H0-CH2-0-CH(R)-CH2CH2-0H, was then identified it undergoes ring closure to the 1,3-dioxane product. Gas-phase Prins reaction of formaldehyde dimer with alkene has been studied computationally it proceeds via a r-complex (without formation of any intermediate rr-complex). ... 

Addition of formaldehyde dimer to alkenes with in the gas phase by the Prins reaction are studied at the MP2(fc)/6-31G(d,p). It is shown that the initially complex obtained at the first study turn into 1,3-dioxane without intermediate formation of a a-complex. Also shown, that transformation of 7i-cation is a pseudo synchronous process. 

In the work we studied some features of formaldehyde oligomers and alkenes interaction resulting in the formation of 1,3-dioxanes. The geometric and orbital structures of the reactions transition states depending on the alkene structure are considered. The following alkenes were used ethylene (1), propylene (2), butene-1 (3), isobutylene (4) and t-butene-2 (5). A formaldehyde dimer (FD) served an example for FO calculation. 

HYDROGENATED PYRANS FORMATION FROM FORMALDEHYDE DIMERS... 

The role of formaldehyde dimer in 0-containing heterocycles formation by the Prins reaction have been investigated. It was shown that the 1,3-di-oxanes, hydrogenated pyrans and oxetanes can be can be obtained from formaldehyde dimers and alkenes in the gas phase. The activation energy of these reactions is different. It is lower for 1,3-dioxanes formation, and higher for oxetanes formation. Thus formation of 1,3-dioxanes happens in the conditions of kinetic control. Opposite, the hydrogenated pyrans formation happens in the conditions of thermodynamic control... 

According to the scheme, formaldehyde dimers preliminary form the corresponding 71-cations (2b-5b) with alkenes (2a-5a), which are isomer-ized into a-cations (2i-5i). These a-cations are transformed through the transition states (2j-5j) into oxetanes (2k-5k). The calculated values of the thermodynamic parameters are represented in Table 11.3. 

Figure 2.13 Observed geometry of the (ethyne, formaldehyde) dimer. (Redrawn from [22] with permission from the Royal Society of Chemistry.)...

In the reaction of the liganded zirconium formaldehyde dimer 80 with excess t-butyl isothiocyanate insertion into both of the Zr-C bonds is observed to give the double insertion product 81 in 83 % yield . 

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