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- Sillrén, Per, 1982, et al.
(author)
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A statistical model of hydrogen bond networks in liquid alcohols
- 2012
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In: Journal of Chemical Physics. - : AIP Publishing. - 1089-7690 .- 0021-9606. ; 136:9, s. 094514-094521
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Journal article (peer-reviewed)abstract
- We here present a statistical model of hydrogen bond induced network structures in liquid alcohols. The model generalises the Andersson-Schulz-Flory chain model to allow also for branched structures. Two bonding probabilities are assigned to each hydroxyl group oxygen, where the first is the probability of a lone pair accepting an H-bond and the second is the probability that given this bond also the second lone pair is bonded. The average hydroxyl group cluster size, cluster size distribution, and the number of branches and leaves in the tree-like network clusters are directly determined from these probabilities. The applicability of the model is tested by comparison to cluster size distributions and bonding probabilities obtained from Monte Carlo simulations of the monoalcohols methanol, propanol, butanol, and propylene glycol monomethyl ether, the di-alcohol propylene glycol, and the tri-alcohol glycerol. We find that the tree model can reproduce the cluster size distributions and the bonding probabilities for both mono- and poly-alcohols, showing the branched nature of the OH-clusters in these liquids. Thus, this statistical model is a useful tool to better understand the structure of network forming hydrogen bonded liquids. The model can be applied to experimental data, allowing the topology of the clusters to be determined from such studies.
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| 2. |
- Sillrén, Per, 1982
(author)
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Hydrogen Bonding in Liquid Alcohols
- 2012
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Licentiate thesis (other academic/artistic)abstract
- Hydrogen bonded (H-bonded) materials, such as water, alcohols, sugars, and even DNA, are extremely important for biology, as well as chemical industry. Alcohols are used as solvents in paints, in perfumes, as cleaners, anti-freezers, or as an alternative to petrol in combustion engines. In medicine, the polymeric alcohol polyethylene glycol, PEG, is used in a process called pegylation, where PEG chains are attached to drugs or therapeutic proteins. Pegylation can prolong the medicines half life in the body, as well as aid in making the drug water soluble.Crucial in most of the applications are the effects the H-bonds have on the physical properties of the liquid and its functionality. H-bonds are intermolecular bonds, with a bond strength corresponding to ∼ 10 times the kinetic energy of the molecule at room temperature. In alcohols and water, this leads to a transient H-bond network, where molecules leaves and joins the networks at picosecond timescales. H-bonding is responsible for intriguing properties, both structural and dynamic. The most well known “anomaly”, is probably the density maximum water exhibits at 4◦ C, but also alcohols have unusual properties, caused by H- bonding, such as the so called Debye process seen in dielectric spectra of mono alcohols.To better understand the effect H-bonds have in different materials, it is im- portant to know what the H-bonded structures look like. This thesis is concerned with the H-bonding structure in some of the simplest H-bonding material: small molecule alcohols. To investigate the structure of the H-bonded clusters we use a combinations of experimental, computational, and theoretical methods. The clusters we have found have a tree-like topology, and a broad distribution of cluster sizes.
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