Hydroxides involving

Extending the reaction times to 3 hours gave a considerably different distribution of products. Not only was the benzothio-phene consumed, but the major product was toluene. These results indicate that the overall reaction of benzothiophene with molten hydroxide involves a ring opening and elimination of a one-carbon fragment to form o-thiocresol (Equation 1), followed by a slower sulfur elimination to form toluene (Equation 2). 

Figure 8.6. Analysis of the energetics of PT in the i, ii, and iii mutants of CA III for the case where the transfer of a proton from residue 64 to the zinc-bound hydroxide involves two water molecules. The figure describes the three states of Eq. (8.40) and considers their change in each of the indicated mutants (relative to the native enzyme), and displays the changes...

The traditional route to sodium hydroxide involved the causticisation of soda ash (Na2C03) with slaked lime [31.22]. This route has largely been superseded by the electrolysis of brine to produce chlorine and caustic soda. However, several companies operating the ammonia soda process or with access to natural sodium carbonate still use the causticisation route [31.23]. 

Thus, both FTIR and in situ XRD results lead to the same conclusion carbon activation with alkaline hydroxides involves a reaction in which the hydroxide (NaOH or KOH) is converted to a carbonate. In addition, XRD shows that the metal (Na or K) is also formed at the highest temperatme. 

In summary, chemical activation by hydroxides involves a main chemical reaction in which carbon atoms are removed from the carbon matrix and are transformed into an inorganic compound (i.e., carbonate), and a subsidiary process in which the metal atoms formed through reduction of hydroxide are thought to be inserted/intercalated between the graphene layers of the residual carbon. This process can play a certain role in the overall activation process, as discussed in the following text. 

FIGURE 21.2 Formation of an oxirane by treatment of a bromohydrin with hydroxide involves an alkoxide acting as a neighboring group. 

Many salt-like halides can be prepared by the action of the hydro-halic acid. HX, on the metal or its oxide, hydroxide or carbonate. The halides prepared by this method are often hydrated, particularly when a less electropositive metal is involved, for example zinc, iron. 

A better method involves the interaction of an alkyl bromide and thiourea to form an alkyl tso-thiourea, followed by hydrolysis of the latter with sodium hydroxide solution, for example ... 

The mechanism of the reaction probably involves the production, by into -action of the aldehyde with hydroxide ions, of two reducing anions, the first (I) more easily than the second (II). Either of these anions may transfer a hydride ion to a carbonyl carbon atom in another aldehyde molecule ... 

The mechanism of the reaction probably involves the intermediate formation ofthe covalent dlazo-hydroxide from the diazonium salt the former decomposes... 

The benzyl group has been widely used for the protection of hydroxyl functions in carbohydrate and nucleotide chemistry (C.M. McCloskey, 1957 C.B. Reese, 1965 B.E. Griffin, 1966). A common benzylation procedure involves heating with neat benzyl chloride and strong bases. A milder procedure is the reaction in DMF solution at room temperatiue with the aid of silver oxide (E. Reinefeld, 1971). Benzyl ethers are not affected by hydroxides and are stable towards oxidants (e.g. periodate, lead tetraacetate), LiAIH, amd weak acids. They are, however, readily cleaved in neutral solution at room temperature by palladium-catalyzed bydrogenolysis (S. Tejima, 1963) or by sodium in liquid ammonia or alcohols (E.J. Rcist, 1964). 

Treating 5.5 g of 2-amino-4,5-dimethylthiazole HCl with 0.66 g of solid sodium hydroxide 15 min at 220°C yields 53% of 4.4. 5.5 -tetramethyT 2,2 -dithiazolylamine, whose structure w as proved by identification with the produa obtained from the reaction between dithiobiuret and 3-bromo-2-butanone (467). This result is comparable to the reaction between 2-aminopyridine and its hydrochloride to yield bis(pyridyl-2)amine (468). Gronowitz applied this reaction to 2-aminothiazole, refluxing it with its hydrochloride 4 hr in benzene and obtained the dimeric 2-aminothiazole (236). He proposed a mechanism (Scheme 143) that involves the addition of a proton to the 5-position of the ring to give 234. The carbocation formed then reacts on the 5-position of a second... 

Hughes and Ingold interpreted second order kinetic behavior to mean that the rate determining step is bimolecular that is that both hydroxide ion and methyl bromide are involved at the transition state The symbol given to the detailed description of the mech anism that they developed is 8 2 standing for substitution nucleophilic bimolecular... 

The last step in the synthesis of divinyl ether (used as an anesthetic under the name Vinethene) involves heating CICH2CH2OCH2CH2CI with potassium hydroxide Show how you could prepare the necessary starting material CICH2CH2OCH2CH2CI from ethylene... 

Two processes that are consistent with second order kinetics both involve hydrox ide ion as a nucleophile but differ in the site of nucleophilic attack One of these processes is an 8 2 reaction in which hydroxide displaces carboxylate from the alkyl group of the ester... 

Once It was established that hydroxide ion attacks the carbonyl group in basic ester hydrolysis the next question to be addressed concerned whether the reaction is concerted or involves a tetrahedral intermediate In a concerted reaction the bond to the leaving group breaks at the same time that hydroxide ion attacks the carbonyl... 

All these facts—the observation of second order kinetics nucleophilic attack at the carbonyl group and the involvement of a tetrahedral intermediate—are accommodated by the reaction mechanism shown m Figure 20 5 Like the acid catalyzed mechanism it has two distinct stages namely formation of the tetrahedral intermediate and its subsequent dissociation All the steps are reversible except the last one The equilibrium constant for proton abstraction from the carboxylic acid by hydroxide is so large that step 4 is for all intents and purposes irreversible and this makes the overall reaction irreversible... 

Many synthetic reactions involving phenols as nucleophiles are carried out m the presence of sodium or potassium hydroxide Under these conditions the phenol is con verted to the corresponding phenoxide ion which is a far better nucleophile... 

MetaUic ions are precipitated as their hydroxides from aqueous caustic solutions. The reactions of importance in chlor—alkali operations are removal of magnesium as Mg(OH)2 during primary purification and of other impurities for pollution control. Organic acids react with NaOH to form soluble salts. Saponification of esters to form the organic acid salt and an alcohol and internal coupling reactions involve NaOH, as exemplified by reaction with triglycerides to form soap and glycerol,... 

Inert Gas Dilution. Inert gas dilution involves the use of additives that produce large volumes of noncombustible gases when the polymer is decomposed. These gases dilute the oxygen supply to the flame or dilute the fuel concentration below the flammability limit. Metal hydroxides, metal carbonates, and some nitrogen-producing compounds function in this way as flame retardants (see Flame retardants, antimony and other inorganic compounds). 

The third process involves careflil addition of aluminum hydroxide to fluorosiUcic acid (6) which is generated by fertilizer and phosphoric acid-producing plants. The addition of Al(OH)2 is critical. It must be added gradually and slowly so that the siUca produced as by-product remains filterable and the AIF. -3H20 formed is in the soluble a-form. If the addition of Al(OH)2 3H20 is too slow, the a-form after some time changes into the insoluble P-form. Then separation of siUca from insoluble P-AIF. -3H20 becomes difficult. 

Alkali Fusion of /u-Benzenedisulfonic Acid. Even though this process like the previous one is a very ancient one, it is still the main route for the synthesis of resorcinol. It has been described in detail previously and does not seem to have drastically evolved since 1980. It involves the reaction of benzene with sulfuric acid to form y -benzenedisulfonic acid which is then converted to its disulfonate sodium salt by treatment with sodium sulfite. In a second step, this salt is heated to 350°C in the presence of sodium hydroxide yielding the sodium resorcinate and sodium sulfite. 

---