Dimethyl ether physical properties

Physical Properties. Industrially, the most important esters are dimethyl malonate [108-59-8] and diethyl malonate [105-53-3] whose physical properties are summarized in Table 2. Both are sparingly soluble in water (1 g/50 mL for the diethyl ester) and miscible in all proportions with ether and alcohol. 

The physical properties of finish removers vary considerably due to the diverse uses and requirements of the removers. Finish removers can be grouped by the principal ingredient of the formula, method of appHcation, method of removal, chemical base, viscosity, or hazardous classification. Except for method of apphcation, a paint remover formulation usually has one aspect of each group, by which it can be used for one or more appHcations. A Hst of the most common organic solvents used in finish removers has been compiled (3). Many are mentioned throughout this article others include ethyl lactate [97-64-3] propylene carbonate [108-32-7] furfural alcohol [98-01-1/, dimethyl formamide [68-12-2] tetrahydrofuran [109-99-9] methyl amyl ketone [110-43-0] dipropylene glycol methyl ether [34590-94-8] and Exxate 600, a trade name of Exxon Chemicals. 

The physical properties of the anhydrate form and two polymorphic monohydrates of niclosamide have been reported [61], The anhydrate form exhibited the highest solubility in water and the fastest intrinsic dissolution rate, while the two monohydrates exhibited significantly lower aqueous solubilities. In a subsequent study, the 1 1 solvates of niclosamide with methanol, diethyl ether, dimethyl sulfoxide, N,/V -dimethyl formamide, and tetrahydrofuran, and the 2 1 solvate with tetraethylene glycol, were studied [62], The relative stability of the different solvatomorphs was established using desolvation activation energies, solution calorimetry, and aqueous solubilities. It was found that although the nonaqueous solvates exhibited higher solubilities and dissolution rates, they were unstable in aqueous media and rapidly transformed to one of the monohydrates. 

Ethers are organic compounds structurally related to alcohols. The oxygen atom in an ether group, however, is bonded not to a carbon and a hydrogen but rather to two carbons. As we see in Figure 12.14, ethanol and dimethyl ether have the same chemical formula, C2H(50, but their physical properties are vastly different. Whereas ethanol is a liquid at room temperature (boiling point 78°C) and mixes quite well with water, dimethyl ether is a gas at room temperature (boiling point —25°C) and is much less soluble in water. 

The oxygen in an alcohol, such as ethanol, is bonded to one carbon atom and one hydrogen atom. The oxygen in an ether, such as dimethyl ether, is bonded to two carbon atoms. Because of this difference, alcohols and ethers of similar molecular mass have vastly different physical properties. 

It s important to realize that different isomers are different chemical compounds. They have different structures, different chemical properties, and different physical properties, such as melting point and boiling point. For example, ethyl alcohol (ethanol, or grain alcohol) and dimethyl ether both have the formula C2H60, yet ethyl alcohol is a liquid with a boiling point of 78.5°C, whereas dimethyl ether is a gas with a boiling point of —23°C. 

High 1,4 B-block ABA copolymers having good physical properties have been reported from l,4-dilithio-l,l,4,4-tetraphenylbutane (84) and 1,4-dilithio-l,4-dimethyl-1,4-tetraphenyIbutane (84) and 1,4-dilithio-1,4-dimethyl-1,4 diphenylbutane (85) initiation. These initiators have been prepared with a minimum of ether (preferably anisole). However, both of these compounds have shown a gradual loss of solubility as a result of association of the alkyllithiums. Attachment of solubilizing oligomeric polydienes apparently alleviated this problem (84, 85). 

No physical properties of 1,2 and 1,3-diazetes have been reported since they are very energtic molecules and can only be detected by spectroscopic means. On the other hand, 1,2- and 1,3-diazetidines have been found to be mostly solids, depending on their substituents. Decomposition has been observed at the melting points of many compounds, especially in the case of 1,3-diazetidines. These compounds are mostly soluble in the usual organic solvents such as ether, chloroform, acetone, etc. However, dimethyl sulfoxide (DMSO) has been used to dissolve diazetidinium salts. Diazetidine derivatives are mostly good solids that can be purified by recrystallization. Liquid compounds can be distilled under reduced pressure without decomposition. 

Hydrogen bonding has a large effect on the physical properties of organic compounds, as shown by the boiling points of ethanol (ethyl alcohol) and dimethyl ether, two isomers of molecular formula C2H60 ... 

Chemical and Physical Properties Trichlorfon is an organophosphate compound, which has an empirical formula of C4HgCl304P and a molecular weight of 257.44. It is a racemic mixture of two isomers. Trichlorfon is a pale clear, white or yellow crystalline powder, melting point 75-84°C, boiling point 100°C, vapor pressure 7.8mmHg at 20°C, and is stable at normal temperatures and pressure. At higher temperatures and pH less than 5.5, trichlorfon decomposes to form dichlorvos (0,0-dimethyl-0-(2,2-dichlorovinyl) phosphate, DDVP). It is readily soluble in chloroform and methylene chloride, and less soluble in water, benzene, and diethyl ether. 

Dimethyl ether (DME) has been used as a fuel and propellant. It is miscible with most organic solvents and is currently under study as a fuel additive for diesel engines due to its high volatility and high cetane number. DME, like other synthetically derived fuels, can be produced from syngas, is essentially sulfur free, contains nearly zero aromatic compounds, and is considered an excellent substitute for conventional diesel and liquefied petroleum gas (LPG). DME has several physical properties similar to those of LPG. 

Physical Properties. Tabun is a colorless compound, which is said to have a somewhat fmity odor. The odor changes with decomposition so that with lesser amounts of decomposition the odor of cyanide (like bitter almonds) is apparent, whereas with greater amounts the odor of dimethyl-amine (like fish) is apparent. Tabun s vapor pressure is the lowest of all the G agents (approximately 0.04 mm Hg at 20°C). This suggests that tabun could be a relatively persistent threat at lower temperatures. Tabun has a vapor density of 5.6 relative to air and a liquid density of 1.08 g/mL (25°C). Its mp is —50°C, and its bp is approximately 240°C. It is three times as water soluble (approximately 10% at 20°C) as is VX, and also soluble in typical organic solvents (e.g., ethanol, diethyl ether, and chloroform). As with other nerve agents, dissolution in inert solvents (e.g., diethyl ether) enhances tabun s stability. 

PHYSICAL PROPERTIES clear, colorless liquid heavy, mobile liquid chloroform-like odor very slightly soluble in water miscible with methanol, ethanol, carbon tetrachloride, benzene, ether, petroleum ether, carbon disulfide, chloroform, dimethyl formamide, and... 

The compound dimethyl ether is a gas with a boiling point of — 24 °C. It is clearly a different substance from ethyl alcohol, differing not only in its physical properties but also in its chemical properties. It does not react at all with sodium metal. Like ethyl alcohol, it reacts with hydriodic acid, but it yields a compound of formula CH3I. Analysisof dimethyl ether show that it contains carbon, hydrogen, and oxygen in the same proportion as ethyl aleohol, 2C. 6H 10. It has the same molecular weight as ethyl alcohol, 46. We conclude that it has.the same molecular formula C2H6O. 

Here we have two substances, ethyl alcohol and dimethyl ether, which have the same molecular formula, C2HgO, and yet quite clearly ire differenteompounds. How can we account for the existence ofithese two compounds The answer is they differ in molecular structure Ethyl alcohol has the structure represented by I, and dimethyl ether the structure represented b)) II. As we shall see, the differenees in physical and chemical properties of thesb two compounds can readily be accounted for on the basis of the difference in structure. 

PPO , that is, poly-2,6-dimethyl-l,4-phenylene ether or PPE, is a high-performance thermoplastic obtained by polymerization of DMP, which exhibits particular physical properties such as high thermal stability, elevated mechanical strength, and excellent hydrolytic stability (Table 7.1) [14]. 

SOME PHYSICAL AND THERMODYNAMIC PROPERTIES OF DIMETHYL ETHER AT VARIOUS TEMPERATURES... 

The specific numerical case used is a ternary mixture of dimethyl ether (DME), methanol (MeOH), and water. The feed composition is 5 mol% DME, 50 mol% MeOH, and 45 mol% water. The feed flow rate is lOOkmol/h, and the feed is fed on Stage 32 of a 52-stage column. The liquid sidestream is withdrawn from Stage 12. The column pressure is set at 11 atm so that cooling water can be used in the condenser (reflux-drum temperature is 323 K with a distillate composition of 98 mol% DME and 2 mol% MeOH). The NRTL physical property package is used. 

In addition to the equipment properties and selected operating conditions, the process performance depends to a large extent on the state of the active solvent component(s). Commonly nsed solvents include physical solvents like methanol (Rectisol) and the dimethyl ethers of polyethylene glycol (Selexol), chemical solvents like aqneous solutions of carbonates such as K2CO3 and Na2C03, of amino acid salts such as mixtures of potassium hydroxide and alanine or tanrine, and especially of alkanolamines such as mono-ethanolamine (MEA), di-ethanolamine (DEA), (activate) methyl-di-ethanolamine (MDEA), di-isopropanolamine (DIPA), di-glycolamine (DGA), 2-amino-2-methyl-l-propanol (AMP), and piperazine (PZ) (1). 

It should be noted that these two isomers are clearly different in their physical properties. At room temperature and 1 atm pressure, dimethyl ether is a gas. Ethanol is a liquid. 

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