Structures alcohol

Chart 1. Experimental reactivity diagrams from piperidino-dehalogenation. Rates relative to a given position (= 1). Reactions in piperidine, structures 25-28 in alcohol, structures 29-31. Data deduced from refs. 18, 20, 29, 42, 43 and 98. 

With ethylenic hydrocarbons, as seen on p.237, it is rather difficult to know whether a dangerous reaction is due to the instability of the double bond or its polymerisation. Allylic alcohol dehydration is one example. Alcohols treated in a sulphuric acid medium can form, according to the conditions and the alcohol structure, either an ethylenic hydrocarbon or an ether. 

Adsorption vs. polymerization, corrosion inhibition, 644-646 27A1 NMR, 127-129 Alcohols, structure, 172/ ... 

The /Tamino alcohol structural unit is a key motif in many biologically important molecules. It is difficult to imagine a more efficient means of creating this functionality than by the direct addition of the two heteroatom substituents to an olefin, especially if this transformation could also be in regioselective and/ or enantioselective fashion. Although the osmium-mediated75 or palladium-mediated76 aminohydroxylation of alkenes has been studied for 20 years, several problems still remain to be overcome in order to develop this reaction into a catalytic asymmetric process. 

It has been shown recently (10) that such block structures could be tailored precisely by the general method summarized hereabove. It is indeed possible to convert the hydroxyl end-group of a vinyl polymer PA (f.i. polystyrene, or polybutadiene obtained by anionic polymerization terminated with ethylene oxide),into an aluminum alcoholate structure since it is well known that CL polymerizes in a perfectly "living" manner by ring-opening insertion into the Al-0 bond (11), the following reaction sequence provides a direct access to the desired copolymers, with an accurate control of the molecular parameters of the two blocks ... 

The zero slope found for transesterification (series 45) can be explained in accordance with the general view on acid-catalyzed reactions of organic acids and esters. The first step is the protonation of the acid or ester, which is followed by interaction with the alcohol (or water in ester hydrolysis). The absence of any observable influence of the alcohol structure on rate indicates that the rate-determining step must be the protonation of the ester. This is in contrast to the homogeneous reaction, in which this step is usually very rapid. The parallel dehydration of the alcohols exhibited a large structure effect on rate (Case 7 from Table II), confirming the independence of the two reaction routes. 

Scheme 10.15 Lactonization of a steroidal homopropargylic alcohol structure.

In this work we extend our study to the hydrogenation and isomerization of a series of a,p-unsaturated alcohols, such as 2-propen-l-ol (A2), (E -2-buten-l-ol (EB2), (" -2-penten-l-ol (ZP2), (E -2-penten-l-ol (EP2), (" -2-hexen-l-ol (ZH2), (E -2-hexen-l-ol (EH2), carried out in the presence of RhCl(PPh3)3, with and without triethylamine (NEts), at 303 K, using ethanol as solvent. The major targets of our research are to investigate the influence of the unsaturated alcohol structure on the product distribution and to verify the possibility of extending the results, previously obtained with (" -2-butene-1,4-diol, to other analogous substrates. 

The propargyl alcohols react with trivalent phosphorus halides to give allenic phosphorus esters as described in Scheme 3 and Table VI. In the case of aryl-substituted alkynols or highly hindered t-propargyl alcohols which contain no free acetylenic —H, thionyl halides or phosphorus trihalides yield bromo- or chloroallenes [74d], Thionyl chloride also reacts in a similar fashion with a wide variety of unhindered secondary alcohols (structure XV) to give a mixture of the chloroallene and chloroalkyne [74a-d]. 

Figure 1. Alcohol structures obtained after isoprene dianionic dimer oxidation hydrogen transfer position (O).

The reactions of thionyl chloride with organic compounds having hydroxyl groups are important. Alkyl chlorides, alkyl sulfites, or alkyl chlorosulfites form from its reaction with aliphatic alcohols, depending on reaction conditions, stoichiometry, and the alcohol structure ... 

In the photocatalytic production of amines from alcohols and ammonia, the efFiciency varied with alcohol structure ethanol > methanol > 2-propanol > t-butanol. A hydrogen atmosphere enhanced the formation of amines, a process which was inhibited by oxygen ... 

The N-acetyl derivative of 4-oxazolin-2-one (395) has been shown to function as a Diels-Alder dienophile (77TL3115, 77LA2027). Reaction of (395) with 2,3-dimethyl-l,3-butadiene took place at 160 °C to furnish the cycloadduct (396) in 97% yield. On heating with methanolic potassium hydroxide, the adduct was converted to the c/s-/3-amino alcohol (397) in high yield (Scheme 87). This oxazolinone thus provides a new entry to the /3-amino alcohol structural unit found in many natural substances. 

As catalytic semihydrogenation of alkynes to Cis-alkenes is not only a very important synthetic operation (ref. 1) but also of industrial interest, it is a challenging task for both synthetic and catalytic chemists. For instance, the importance of the problem is illustrated by numerous recent publications on different aspects of the selective hydrogenation of many compounds related to the propargyl alcohol structure (refs. 2-7). In this respect, 1,4-butenediol, obtained by the liquid-phase semihydrogenation of 1,4-butynediol, is a raw material for insecticides and Vitamin Bg (refs. 2,8,9). Furthermore, the total and selective liquid-phase hydrogenation of this compound is one of the procedure for making butanediol, the top 95 chemical produced in the United States (refs. 10,11), whose major use is in the manufacture of polyesters. 

Figure 2 shows a difference curve obtained from methylol kraft lignin when untreated lignin was used as reference. The difference curve has a distinct maximum at 590 m/z, characteristic of the phenol alcohol structures formed. By comparing the absorbance at 590 m/z with the molar absorbance (e) of models investigated, the amount of phenol alcohols in lignin can be estimated. The numerical values depend somewhat on the e value of the model chosen. In this study a value of e = 840 was used, the increase found at 590 m/z between the molar absorbances of the dimeric phenol alcohol and its parent phenol of model II. 

When (PPh3)3PdCl2 is used as the catalyst precursor and optically active alcohols are used as the hydrogen donors, a small asymmetric induction occurs (see Table II) which could be due to a solvent effect (25). However, the large influence of the alcohol structure on re-gioselectivity suggests that the alcohol residue is present in (at least one of) the catalytic complexes. 

Raman Spectroscopic Evidence for Coniferyl Alcohol Structures in Bleached and Sulfonated Mechanical Pulps... 

---