Excess heats of tri-n-alkylamines and tetraalkyl tin compounds in linear and branched alkanes: correlations of molecular orientations and steric hindrance effect

1979 ◽  
Vol 57 (5) ◽  
pp. 517-525 ◽  
Author(s):  
R. Philippe ◽  
G. Delmas ◽  
Phuong Nguyen Hong
Keyword(s):  
Steric Hindrance ◽  
Solution Structure ◽  
The Other ◽  
Short Chain ◽  
Flory Theory ◽  
Tin Compounds ◽  
Branched Alkanes ◽  
Linear Alkanes ◽  
Chain Compounds ◽  
Long Chain

Excess heats of the following mixtures of trialkylamines and tetraalkyl tin compounds with branched and linear alkanes have been measured at 25 °C: five trialkylamines NR3 (R = C2H5, C3H7, C4H9, C10H21, C12H25) with six linear alkanes, n-C5, n-C6, n-C8, n-C10, n-C12, n-C16, and three highly branched alkanes, 2,2,4-trimethylpentane, 2,2,4,6,6-pentamethylheptane, and 2,2,4,4,6,8,8-heptamethylnonane (br-C16). Further measurements were carried out on tetrapropyl tin (SnPr4) with n-C8, n-C16, and br-C16.Measurements were made to obtain more information on the heats of disordering of long chain compounds and on an exothermic contribution to the heats coming possibly from the sterically hindered character of one of the components of the mixture. The three short-chain trialkylamines have large heats with the linear long alkanes and small heats with the branched alkanes. On the other hand, the two long-chain trialkylamines have very small heats with linear alkanes and large heats with the branched alkanes. These results are interpreted as indicating no change of liquid or solution 'structure' when two ordered compounds (long alkanes and long-chain amines) are mixed but a change of 'structure' when an ordered compound (long alkane or long-chain amine) is mixed with a non-ordered one (branched alkane or short-chain amine). The heat of disordering of n-hexadecane is obtained with many order breakers and found to depend to some extent on the expansion coefficient of the order breaker. HE values for the series of the shorter NR3 do not vary regularly with molecular weight but are smaller for the propyl (and possibly the ethyl) derivative. Similarly, HE of SnPr4 in n-C16, br-C16, and n-C8 are much lower than the corresponding heats with SnEt4 and SnBut4. This is attributed to the presence of the exothermic contribution to the heats, HE(steric hindrance). The X12 parameter of the Flory theory has been calculated and is interpreted in terms of the disorder and steric hindrance contributions to the heats.

Excess heat capacities and excess volumes of tetraalkyltin compounds: . Effect of correlations of molecular orientations and steric hindrance. Part 1

1984 ◽  
Vol 62 (6) ◽  
pp. 1008-1015 ◽  
Author(s):  
Bernard Riedl ◽  
Geneviève Delmas
Keyword(s):  
Steric Hindrance ◽  
Central Atom ◽  
Orientational Order ◽  
Excess Volumes ◽  
Pure Liquid ◽  
Flory Theory ◽  
Flow Calorimeter ◽  
Alkyl Chains ◽  
Chain Compounds ◽  
Long Chain

A Picker flow calorimeter has been used to obtain molar excess capacities [Formula: see text] through the concentration range at 25 °C for the systems [Formula: see text] where R is the alkyl group CnH2n+1, (n = 1, 2, 3, 4, 8, 12). Excess volumes have also been measured for the mixtures. Two contributions to [Formula: see text] and vE were investigated: those associated with disordering the long alkyl chains and with steric hindrance. The steric hindrance contribution has been found to occur for molecules having a highly substituted central atom. The sign of this contribution is negative in hE and positive in [Formula: see text], indicative of an ordering or loss of mobility for the molecules going from pure liquid to solution. The [Formula: see text] results confirm the more sterically hindered character of the ethyl and propyl derivatives already found with hE. The separation of the disorder and steric contribution is possible in systems involving long-chain compounds. It is found that the orientational order contribution diminishes more slowly with temperature than the steric hindrance effect. The trend of vE in the series is reasonably well predicted by the Prigogine–Patterson–Flory theory.

Heats of mixing of trialkylamines: disorder and steric hindrance contributions

1978 ◽  
Vol 56 (22) ◽  
pp. 2856-2865 ◽  
Author(s):  
Robert Philippe ◽  
Geneviève Delmas ◽  
Phuong Nguyen Hong
Keyword(s):  
Steric Hindrance ◽  
Significant Contribution ◽  
Orientational Order ◽  
Class A ◽  
Heats Of Mixing ◽  
Class B ◽  
Chain Compounds ◽  
Sterically Hindered ◽  
Long Chain ◽  
Long Chains

Nine trialkylamines, triethyl- to trihexylamine trioctyl-, tridodecyl, tri(methyl-2-butyl)-, and dimethyldodecylamine have been used for heats of mixing of the following systems at 298 K: A, fourteen systems made of all the possible binary mixtures (except one) of the six shorter amines; B, twelve systems made of a long chain amine, trioctyl-, tridodecyl- or dimethyldodecylamine with the four shorter members of the series; C, two systems consisting of the mixture of two long-chain compounds, trioctylamine with tridodecyl- and dimethyldodecylamine. Heats for the class A systems are less than or equal to 40 J/mol, indicating no net effect of the small polarity of the shorter members of the series. The experimental HE of these mixtures are compared with two theories. The Monte Carlo approach gives good predictions but the heats calculated with the Snider–Herrington theory are too negative. Heats of the class B systems are suitable for the investigation of two new contributions to the heats of mixing, the positive heat of disordering of long-chains HE(dis.) and the negative heat found in systems where one of the components is sterically hindered, HE(ster.hindr.). HE(dis.) found with the long-chain amines indicates an orientational order larger than in the case of the n-alkane of the same chain-length but equivalent to that found in the tetraalkyltin compounds of the same length. Recent work has shown that the tetrapropyl and tetraethyltin derivatives when mixed with long-chain alkanes or tin derivatives give rise to a HE(ster.hindr.) contribution. From this work and the present study, the steric hindrance contributions of five sterically hindered compounds tetraethyltin and tetrapropyltin, triethyl- and tripropylamine, and 3,3-diethylpentane mixed with different second components are calculated. The steric hindrance contribution is found proportional to the volume of the second component and increasing in the following order of the sterically hindered component: triethyl- < tripropylamine < tetraethyl- < tetrapropyltin < 3,3-diethylpentane. Heats of the class C systems are small without significant contribution of HE(dis.) due to the fitting of the long-chains in solution.

Excess thermodynamic properties of tetraalkyltin compounds with Trans-decalin and highly branched alkanes. Effect of steric hindrance

1986 ◽  
Vol 64 (4) ◽  
pp. 681-688 ◽  
Author(s):  
Hong Phuong-Nguyen ◽  
Geneviève Delmas
Keyword(s):  
Thermodynamic Properties ◽  
Steric Hindrance ◽  
Thermodynamic Quantities ◽  
Flory Theory ◽  
Excess Viscosities ◽  
Branched Alkanes ◽  
Energy Of Mixing ◽  
Excess Thermodynamic Quantities ◽  
The Difference ◽  
Free Energy Of Mixing

Molar excess thermodynamic quantities hE, [Formula: see text], and vE have been measured at 25 °C over the whole composition range for mixtures of four globular Sn(CnH2n+1)4 (SnR4) (n = 1–4) with t-decalin, and 2,2,4,4,6,8,8-heptamethylnonane (br-C16) as well as hE for the same SnR4 compounds with 2,2,4-trimethylpentane (br-C8). The excess viscosities are measured at −20, 25, and 40 °C for the t-decalin + SnR4 systems. By introducing gE in the solution activation energy, the free energy of mixing can be related to and calculated from the excess viscosities. The steric hindrance contribution, corresponding to an increase of order or diminution of mobility in solution, known to occur either with compounds having highly substituted atoms or with flat-shaped molecules, was investigated. The free volume contribution to the different thermodynamic properties is calculated from the Prigogine–Patterson–Flory theory. The difference between the experimental and calculated excess data is associated with the steric hindrance contribution. Values of hE, [Formula: see text], vE, and sE confirm the existence of a large steric hindrance contribution (hE < −200 J mol−1 and TsE < −400 J mol−1 for two systems). Another contribution, found to occur for the two smaller globular SnR4, may originate in the liberation of movement induced in solution by the second component.

scholarly journals Competition between hydrogen bonding and dispersion interactions in the crystal structures of the primary amines

CrystEngComm ◽  
2014 ◽  
Vol 16 (19) ◽  
pp. 3867-3882 ◽  
Author(s):  
Andrew G. P. Maloney ◽  
Peter A. Wood ◽  
Simon Parsons
Keyword(s):  
Hydrogen Bonding ◽  
Crystal Structures ◽  
Crystal Packing ◽  
Short Chain ◽  
Primary Amines ◽  
Dispersion Interactions ◽  
Chain Compounds ◽  
The Cross ◽  
Long Chain

In the short chain amines H-bonding dominates crystal packing, but dispersion wins-out for the long chain compounds. The cross-over point occurs between butyl and pentylamine, where interactions are finely balanced.

Heats and free energies of mixing of tridodecylamine with nine heptane isomers, two octanes, and one hexane. Disorder and steric hindrance contributions

1978 ◽  
Vol 56 (18) ◽  
pp. 2472-2479 ◽  
Author(s):  
Michèle Couchon ◽  
Phuong Nguyen Hong ◽  
Genevieve Delmas
Keyword(s):  
Steric Hindrance ◽  
Free Energies ◽  
Negative Contribution ◽  
Flory Theory ◽  
Class A ◽  
Heats Of Mixing ◽  
Linear Alkanes ◽  
Class B ◽  
Class C ◽  
Branched Isomer

Heats and free energies of mixing have been measured at 298 K for tridodecylamine in n-C7, and eight branched isomers, n-C8 and one branched isomer, and a branched hexane. Heats of mixing are such that these systems can be divided in three classes. Class A [Formula: see text] includes n-C7, and n-C8. Class B [Formula: see text] includes isomers which do not have two substituents on neighbouring carbon atoms, i.e. 2-MeC6 2,2-diMeC5, 2,4-diMeC5, 2,2,4-triMeC5. Class C which includes isomers having substituents on neighbouring carbon atoms; 2,3-diMeC5, 2,2,3-triMeC4, 3-MeC6, 3,3-diMeC5, 3-EtC5, has smaller values of heats of mixing [Formula: see text]. These results are interpreted as not showing an extensive destruction of the correlations of orientations of the dodecyl chains by the linear alkanes of class A. The larger heats of class B are indicative of more disorientations of the long chains by the globular isomers. The smaller values of the heats for class C are seen as the balance of a positive disordering contribution and a negative one. The negative contribution is associated with a sterically hindered character of the compounds having substituents on neighbouring atoms. Free energies of mixing do not separate in the same three classes. This is thought to be due to an enthalpy–entropy compensation in the disordering and steric hindrance contributions. The Xl2S1−l parameter of the Flory theory shows the same variation as HE.

Regioselectivity of nucleophilic aromatic photosubstitution in the biphenyl series. Photohydrolysis of some dimethoxynitrobiphenyls

1987 ◽  
Vol 52 (10) ◽  
pp. 2482-2491 ◽  
Author(s):  
Ján Urban ◽  
Petr Kuzmič ◽  
David Šaman ◽  
Milan Souček
Keyword(s):  
Nitro Group ◽  
Steric Hindrance ◽  
The Other ◽  
Quantum Yields ◽  
Hydroxide Anion ◽  
Tert Butanol ◽  
Nitro Derivatives

Anaerobic photolysis of dimethoxynitrobiphenyls IIIa-VIa in aqueous alkaline tert-butanol gave products of nucleophilic photosubstitution of methoxyl by hydroxide anion, while the dimethoxybiphenyls Ia and IIa were found unreactive. Regioselectivity of the reaction was examined in view of a possible “extended meta activation” by the nitro group. The most reactive substrate IIIa gives both C-3 and C-4 substitution products with an unsubstantial preference for the latter, which opposes the “extended meta selectivity” rule. All of the other compounds obey the rule, and 3,4-dimethoxy-3'-nitrobiphenyl (IVa) even displayed absolute selectivity by yielding C-3 substituted compound as the only product. 2,5-Dimethoxy substituted compounds underwent photosubstitution which much lower quantum yields than their 3,4-substituted counterparts, most probably due to some steric hindrance of conjugation. Similarly, 3-nitro-substituted biphenyls exhibited much lower overall reactivity than 4-nitro derivatives.

scholarly journals Stereospecific Hydroxylation of Long Chain Compounds by a Species of Torulopsis

1969 ◽  
Vol 244 (4) ◽  
pp. 882-888 ◽  
Author(s):  
E Heinz ◽  
A P Tulloch ◽  
J F T Spencer
Keyword(s):  
Chain Compounds ◽  
Long Chain

scholarly journals The absorption of stearic acid from triacylglycerols: an inquiry and analysis

2000 ◽  
Vol 13 (2) ◽  
pp. 185-214 ◽  
Author(s):  
Geoffrey Livesey
Keyword(s):  
Fatty Acids ◽  
Body Weight ◽  
Melting Point ◽  
Cocoa Butter ◽  
Stearic Acid ◽  
Short Chain ◽  
Apparent Digestibility ◽  
Long Chain Fatty Acids ◽  
Long Chain ◽  
Chain Fatty Acids

AbstractAlthough stearic acid is a saturated fatty acid, its influence on plasma cholesterol acid other health variables is neutral; possibly owing in part to poor absorption. Reduced absorption of stearic acid from particular triacylglycerols, cocoa butter and novel fats formulated with short- and long-chain acid triacylglycerol molecules (Salatrims) has been attributed to high intakes. However, the circumstances and causes of poor stearic acid digestion from triacylglycerols are unclear; published data were therefore collected and analysed, with emphasis on human studies. Of twenty-eight studies conducted in adults, most are in men (>90%). The assertion that reduced absorption is due to a high intake of stearoyl groups is not supported: dietary intakes of stearoyl of 0·05–0·65 g stearic acid equivalent/kg body weight (cf typical intake of 0·2 g stearic acid equivalent/kg body weight in the Western diet) indicate that the ‘true’ digestibility of stearoyl is 0·98 (SE 0·01) g/g, with apparent digestibility less than this value at low intakes owing to endogenous stearic acid excretion and to inter-publication variation of unidentified cause. The neutral health impact of stearic acid must be due to factors other than availability. Exceptions include cocoa butter, Salatrims and tristearin, for which digestibility is an additional factor. The efficiency with which human subjects digest stearoyl from cocoa butter still remains uncertain, while the digestion of total long-chain fat from this source is 0·89–0·95 g/g, high in comparison with 0·33 g/g for Salatrim 23CA and 0·15 g/g for tristearin in their prepared states. Salatrims contain the highest proportion of long-chain fatty acids that are stearic acid-rich other than tristearin, which is the main component of fully-hydrogenated soyabean and rapeseed oil. Analysis shows that apparent digestibility of stearic acid is associated with stearoyl density within the triacylglycerol molecule and that, in Salatrims, the occurrence of short-chain fatty acids in place of long-chain fatty acids increases this density. Soap formation appears not to be a major factor in the reduced digestion of stearic acid from tristearin under regular dietary circumstances, but both microcrystallinity and reduced digestibility of tri-, di- and monostearoylglycerols appears to be important. Solubilisation of high-melting-point tristearin in low-melting-point oils improves the digestibility of its stearic acid, particularly when emulsified or liquidized at above melting point. However, without such artificial aids, the digestive tracts of the rat, dog and man have a low capacity for emulsifying and digesting stearic acid from tristearin. Reduced digestibility of stearic acid from Salatrim 23CA also appears to be attributable to reduced digestibility of di- and monostearoylglycerols and is particularly due to remnants with the 1- or 3-stearoylglycerol intact after initial hydrolytic cleavage. Short-chain organic acid in Salatrim 23CA, which is readily hydrolysed, leaves such remnants. Unlike tristearin, Salatrim 23CA melts at body temperature and mixing it with low-melting-point oils is not expected to cause further disruption of microcrystalline structures to aid digestibility of its stearoyl groups. The low digestibility of stearoyl in Salatrim 23CA, together with the occurrence of short-chain organic acids in this product, account for its relatively low nutritional energy value (about 20 kJ (5 kcal)/g) compared with traditional fats (37 kJ (9 kcal)/g) and low fat value (<20:37 kJ/kJ; <5:9 kcal/kcal) relative to traditional fats. In part these differences are because of minor effects of Salatrim 23CA on the excretion of other fat and protein, due to the bulking properties of this poorly-digestible fat.

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