1 Classification reactions Ethers

There is no unity of opinion in the literature concerning a classification, i.e, whether to call these transformations aza-Claisen or aza-Cope rearrangements. It is accepted that the term aza-Claisen should be reserved only for those processes in which a carbon atom in the allyl vinyl ether system has been replaced by nitrogen357. Three different types of aliphatic 3-aza-Cope reactions which were studied theoretically are the rearrangements of 3-aza-l,5-hexadienes (610, equation 262), 3-azonia-l,5-hexadienes (611, equation 263) and 3-aza-l,2,5-hexatrienes (612, equation 264) (the latter is a ketenimine rearrangement )357. 

As was the case for the alkyl hydroperoxides in reaction 4, the enthalpies of the oxy-gen/hydrocarbon double exchange reaction 8 for dialkyl peroxides are different depending on the classification of the carbon bonded to oxygen. For R = Me, Et and f-Bu, the liquid phase values are —4, 24.6 and 52.7 kJmoR, respectively, and the gas phase values are 0.1, 25.7 and 56.5 kJmoR, respectively. For the formal deoxygenation reaction 9, the enthalpies of reaction are virtually the same for dimethyl and diethyl peroxide in the gas phase, —58.5 0.6 kJ moR. This value is the same as the enthalpy of reaction of diethyl peroxide in the liquid phase, —56.0 kJ moR (there is no directly determined liquid phase enthalpy of formation of dimethyl ether). Because of steric strain in the di-ferf-butyl ether, the enthalpy of reaction is much less negative, but still exothermic, —17.7 kJmol (Iq) and —19.6 kJmol (g). 

Some criticism (23, 24, 34) of our previously presented results does not consider all the kinetic data obtained recently in the systematic study of such families as alkylaromatics, ethers, alcohols. Taken together, the cross tests permitted classification of many of the compounds studied by substituent as well as by relative kt values. This arrangement is shown in Table II. Once this was done, all that remained was to standardize the absolute value of this classification and to check its accuracy. For this purpose, we used several values of kt available from the literature for the compounds studied. Table III lists these values corrected to 60°C., where the authors gave an activation energy measurement for the recombination reaction, but otherwise listed without correction. Considering the slight variation of these constants with temperature they are... 

Classification and Organization of Reactions Forming Difunctional Compounds. This chapter considers all possible difunctional compounds formed from the groups acetylene, carboxylic acid, alcohol, thiol, aldehyde, amide, amine, ester, ether, epoxide, thioether, halide, ketone, nitrile, and olefin. Reactions that form difunctional compounds are classified into sections on the basis of the two functional groups of the product. The relative positions... 

DOT CLASSIFICATION Forbidden SAFETY PROFILE A poison. Can explode spontaneously. The solid, liquid and vapor are shock-sensitive explosives. Concentrated solutions in organic solvents may explode. Moderate fire hazard in the form of vapor by chemical reaction. A powerful oxidant. Moderately explosive when exposed to heat. The liquid explodes on contact with arsenic, sodium, silver foil, or phosphorus. Incompatible with Sb, ethyl ether, Ag, metals. When heated to decomposition it... 

DOT CLASSIFICATION Forbidden SAFETY PROFILE A severe explosion hazard when shocked, exposed to heat or flame, or by spontaneous chemical reaction. It has no known uses as an explosive because it is far too sensidve in the dry state to store or handle safely. If this material must be worked with, it should be kept wet. A convenient way of keeping it wet is with ether when it is needed in the dry state, it simply has to be taken out into the open and the ether wiU evaporate, leaving it perfecdy dry. When dry, it will explode when given the slightest touch, vibradon, or rise in temperature. Even a puff of air directed into it can cause it to detonate. It is a high explosive and is very violent. Incompadble with O3. H2S, CI2, Br2, acids. See also IODIDES. 

DOT CLASSIFICATION 5.1 Label Oxidizer SAFETY PROFILE Moderately toxic by intraperitoneal route. Severe skin and eye irritant. A powerful oxidizer which has caused many explosions in industry. Potentially explosive reactions with alkenes (above 220°C), ammonia, arjl hydrazine + ether, dimethyl sulfoxide + heat, ethylene oxide, fluorobutane + water, organic materials, phosphorus, trimethyl phosphate. Reacts to form explosive products with ethanol (forms ethyl perchlorate), cellulose + dinitrogen tetraoxide + oxygen (forms cellulose nitrate). Avoid contact with mineral acids, butyl fluorides, hydrocarbons. A drying agent. When heated to decomposition it emits toxic fumes of MgO and Cr. See also MAGNESIUM COMPOUNDS and PERCHLORATES. 

In our previous discussion of the elementary steps involved in chemical reactions we used the decomposition of diethyl ether as an example of a chain reaction in which a cycle of elementary steps produces the final products. Many reactions are known to occur by chain mechanisms, and in the following discussion we refer primarily to those that generally correspond to the closed sequence in the classification of Boudart. Here active centers (also called active intermediates or chain carriers) are reacted in one step and regenerated in another in the sequence however, if we look back to reaction (IV) a closer examination discloses that some of the steps have particular functions. In (IVa) active centers are formed by the initial decomposition of the ether molecule, and in (IVd) they recombine to produce the ether. The overall products of the decomposition, C2H6 and CH3CHO, however, are formed in the intermediate steps (IVb) and (IVc). In analysis of most chain reactions we can think of the sequence of steps as involving three principal processes ... 

It is convenient in the classification of general schemes such as (IX) to characterize the chain by both the number of active centers involved and the order of the chain termination step. Thus, (XI) would be referred to as a chain with a single active center and second-order termination. The ether decomposition reaction we have discussed is a chain with two active centers and second-order termination, first-order with respect to each of the active centers. In general notation ... 

Saturated Aliphatic Compounds Containing Heteroatoms. A great variety of organic matter falls in this classification—for example, alcohols, ethers, mercaptans, amines, and halides. Two types of simple cleavage reactions may occur that are initiated or directed by the presence of the heteroatom (O, S, N, X, etc.), as exemplified by Equations 16.18 and 16.19 for ethyl ether. Heteroatoms that can stabilize the positive... 

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