Addition of Alcohols

Alcohols can be added to aldehydes in the presence of an anhydrous acid catalyst. The alkoxide part (RO-) of the alcohol is attached to the carbon atom of the carbonyl group of the aldehyde and the proton (H+) from the alcohol is attached to the oxygen of the aldehyde. The new compound is called a hemiac-etal. 

HCN is a very harmful toxic gas. The frightening thing is that its odor can be noticed only when it reaches deadly levels. 

Acetals do not react with same reactants as aldehydes because the ether bonds in acetals give them a different structure. 

Millipedes spray a toxic gas to protect themselves. They carry mandelanitrile (benzaldehyde cyanohydrine) in their protective glands. When they are attacked, cyanohydrine and an enzyme are mixed to produce benzaldehyde and HCN. This is then sprayed at the attacker. A millipede can spray enough HCN to kill a mouse. 

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The most satisfactory reagent is a saturated solution of sodium bisulphite containing some alcohol it must be prepared aa required since it oxidises and decomposes on keeping. Frequently, a saturated aqueous solution is used without the addition of alcohol. 

Addition of nucleophiles to both activated and unactivated alkenes is catalyzed by Pd(II). Addition of alcohols or AcOH to alkenes bearing EWGs is catalyzed by PdCl2(PhCN)2 to give the corresponding ethers and esters. The addition of an alcohol to the cyclic acetal of acrolein 82 to give the ether 83 is also possible with the same catalyst[64]. Amines add to the vinylic ether 84 to give 85, but not to simple alkenes[65]. 

Acid catalyzed addition of alcohols to alkenes is sometimes used Indeed before Its use as a gasoline additive was curtailed billions of pounds of tert butyl methyl ether (MTBE) was prepared by the reaction... 

Reactions with Alcohols. The addition of alcohols to acrolein may be catalyzed by acids or bases. By the judicious choice of reaction conditions the regioselectivity of the addition maybe controlled and alkoxy propionaldehydes, acrolein acetals, or alkoxypropionaldehyde acetals produced in high yields (66). 

The addition of alcohols to form the 3-alkoxypropionates is readily carried out with strongly basic catalyst (25). If the alcohol groups are different, ester interchange gives a mixture of products. Anionic polymerization to oligomeric acrylate esters can be obtained with appropriate control of reaction conditions. The 3-aIkoxypropionates can be cleaved in the presence of acid catalysts to generate acrylates (26). Development of transition-metal catalysts for carbonylation of olefins provides routes to both 3-aIkoxypropionates and 3-acryl-oxypropionates (27,28). Hence these are potential intermediates to acrylates from ethylene and carbon monoxide. 

Important side reactions are the formation of ether and addition of alcohol to the acrylate to give 3-alkoxypropionates. In addition to high raw material costs, this route is unattractive because of large amounts of sulfuric acid—ammonium sulfate wastes. 

Citral readily forms acetals by acid-catalyzed addition of alcohols or by the use of trialkoxyorthoformates. Citral dimethyl acetal [7549-37-3] is stable under alkaline conditions, whereas citral is not. Neryl and geranyl nitriles can be made by oximation of citral and dehydration of the intermediate oxime. For instance, geranonitrile [31983-27-4] is made as follows ... 

Living VE polymerization is usually terminated by addition of alcohols, phenols, amines, etc, that can replace iodide. Without some base present to neutralize generated HI, an aldehyde end group forms if moisture is present because of acid-catalyzed hydrolysis (41). 

Barium hydro sulfide [25417-81-6], Ba(HS)2, is formed by absorption of hydrogen sulfide into barium sulfide solution. On addition of alcohol, barium hydrosulfide tetrahydrate [12230-74-9], Ba(HS)2 4H2O, crystallizes as yellow rhombic crystals that decompose at 50 °C. Sohd barium hydro sulfide is very unstable. Its solubility in water is... 

Addition of alcohols and phenols ia the presence of anhydrous hydrogen chloride gives 0-substituted pseudourea salts (17). The reaction is sluggish except with the lower alcohols, and long reaction time and temperatures up to 100°C are requited to obtain good yields. 

Characterised by conversion to the acridine salt by addition of alcoholic acridine (l.lg in 50mL), filtering off the yellow salt and recrystallising from H2O. The salt has m 215°(dec), A- ax 259nm (e 15,400) in H2O. [Baddiley and Todd J Chem Soc 648 1947, 582 1949, cf LePage Biochem Prep 1 1 I949 Martell and Schwarzenbach Helv Chim Acta 39 653 7956]. 

Strong acids also catalyze the addition of alcohols to alkenes to give ethers, and the mechanistic studies which have been done indicate that the reaction closely parallels the hydration process. ... 

SECTION 8.1. HYDRATION AND ADDITION OF ALCOHOLS TO ALDEHYDES AND KETONES... 

The equilibrium constants for addition of alcohols to carbonyl compounds to give hemiacetals or hemiketals show the same response to structural features as the hydration reaction. Equilibrium constants for addition of metiianoHb acetaldehyde in both water and chloroform solution are near 0.8 A/ . The comparable value for addition of water is about 0.02 The overall equilibrium constant for formation of the dimethyl acetal of... 

In the manufacture of pure resorcinol resins, the reaction can be violently exothermic unless controlled by the addition of alcohols. Because the alcohols perform other useful functions in the glue mix, they are left in the liquid adhesive. PRF adhesives are generally prepared firstly by reaction of phenol with formaldehyde to form a PF resol polymer, that has been proved to be in the greatest percentage, and often completely, linear [95], In the reaction step that follows the resorcinol chemical is added in excess to the PF-resol to react it with the PF-resin -CH2OH groups to form PRF polymers in which the resorcinol groups can be resorcinol chemical or any type of resorcinol-formaldehyde polymer. 

Cross-conjugated dienones are quite inert to nucleophilic reactions at C-3, and the susceptibility of these systems to dienone-phenol rearrangement precludes the use of strong acid conditions. In spite of previous statements, A " -3-ketones do not form ketals, thioketals or enamines, and therefore no convenient protecting groups are available for this chromophore. Enol ethers are not formed by the orthoformate procedure, but preparation of A -trienol ethers from A -3-ketones has been claimed. Another route to A -trien-3-ol ethers involves conjugate addition of alcohol, enol etherification and then alcohol removal from la-alkoxy compounds. 

Miller et al. [9] hypothesized rules on the regioselectivity of addition from the study of the base-catalyzed addition of alcohols to chlorotnfluoroethylene. Attack occurs at the vinylic carbon with most fluorines. Thus, isomers of dichloro-hexafl uorobutene react with methanol and phenol to give the corresponding saturated and vinylic ethers The nucleophiles exclusively attack position 3 of 1,1-dichloro-l,2,3,4,4,4-hexafluoro-2-butene and position I of 4,4-dichloro-l,l,2,3,3,4-hexafluoro-1-butene [10]. In I, l-dichloro-2,3,3,4,4,4-hexafluoro-l-butene, attack on position 2 is favored [J/] (equation 5) Terminal fluoroolefms are almost invariably attacked at tbe difluoromethylene group, as illustrated by the reaction of sodium methoxide with perfluoro-1-heptene in methanol [/2J (equation 6). 

Another major use of organotin compounds is as curing agents for the room temperature vulcanization of silicones the 3 most commonly used compounds are Bu2SnX2, where X is acetate, 2-ethylhexanoate or laurate. The same compounds are also used to catalyse the addition of alcohols to isocyanates to produce polyurethanes. 

From the above table the ideal period of maceration is two hours. Having once added the alcohol to arrest fermenlatioo, the lime the liquid is allowed to stand before distillation seems to hare no iufluence npon the results nfler the two hours maccralion and addition of alcohol, it was allowed txj stand cvtvnigbt. 

We have recently shown that the hydrophobic hexafluorophosphate ILs can in fact be made totally miscible with water by addition of alcohols [47, 48] the ternary phase diagram for [BMIM][PF(3]/water/ethanol (left part of Figure 3.3-7) shows the... 

The presence of alcohols in the aqueous medium generally decreases grafting. This is expected since the addition of alcohol breaks the tetrahedral hydrogen bonded structure of water and thus disturbs the association of active sites with water. This will lead to a decrease in grafting. In the presence of alcohols, chain... 

ADDITION OF ALCOHOLS TO ISOBUTYLENE (Methyl- and Ethyl-Ter-Butyl Ether)... 

The results obtained by measuring the affinity to oxygen in the presence of various monohydric alcohols (methanol, ethanol, 2-propanol, 1-propanol) 140-144> were interpreted in terms of the Monod-Wyman-Changeux model145), by which the change of the standard free-energy difference between R and T state in the absence of oxygen, due to the addition of alcohol, can be determined, i.e. 

Nucleophilic addition of an alcohol to the carbonyl group initially yields a hydroxy ether called a hemiacetal, analogous to the gem diol formed by addition of water. HcmiacetaJs are formed reversibly, with the equilibrium normally favoring the carbonyl compound. In the presence of acid, however, a further reaction occurs. Protonation of the -OH group, followed by an El-like loss of water, leads to an oxonium ion, R2C=OR+, which undergoes a second nucleophilic addition of alcohol to yield the acetal. The mechanism is shown in Figure 19.12. 

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