General reaction

General Reactions.—A full account of the synthesis of thiirans from aldehydes and ketones using metalated 2-(alkylthio)-2-oxazolines has appeared. Asymmetric syntheses of chiral thiirans can be effected using either a chiral oxazoline or a chiral dialkyl dithiocarbonate.  

A new method of synthesis of substituted cyclohex-1-enyl alkyl sulphides involves the reaction of the appropriate cyclohexanone with a thioacetal or thiol in the presence of aluminium chloride.Aldehydes and ketones give symmetrical dialkyl disulphides on treatment with hydrogen sulphide in the presence of pyridine and triethylamine.  

5-Substituted v-butyrolactones can be prepared by reaction of aldehydes or ketones with tbe dianion (28), and direct condensation of symmetrical ketones with diethyl 2-oxomalonate provides a useful synthetic route to the butenolides (29). A number of initiators have been used previously to promote the free-radical addition of ketones to alkenes now transition-metal oxides have been shown to be effective. Pent-4-enal is cyclized to cyclopentanone by chlorotris(triphenylphos-phine)rhodium(i) through a non-radical pathway.  

The efficiency of homoailyl alcohol production following the simultaneous passage of an allylic bromide and a carbonyl compound through a heated column of granular zinc has been used in the synthesis of ( )-artemesia alcohol (30).  

Hosomi and H. Sakurai, Tetrahedron Letters, 1976, 1295 G. Deleris, J. Dunogues, and R. Calas, ibid., p. 2449. 

General Reactions.—A forgotten carbonyl reaction, namely halogenoacylation of aliphatic ketones and aliphatic a,/3-unsaturated and aromatic aldehydes has been reinvestigated [equation (15)]. °  

Kobayashi, and T. Mukaiyama, Bull. Chem. Soc. Japan, 1978, 51, 1869. T. Mukaiyama, K. Soai, and S. Kobayashi, Chem. Letters, 1978, 219. 

Neuenschwander, P. Bigler, K. Christen, R. Iseli, R. Kyburz, and H. Muhle, Helv. Chim. Acta, 1978, 61, 2047 see also P. Bigler, S. Schonholzer, and M. Neuenschwander, ibid., p. 2059. 

A novel zinc-promoted coupling of three components, namely alkyl halides, activated alkenes, and carbonyl compounds, is characterized by remarkable simplicity and high yield [equation (16)].  

RCHO + CHCI3 RCH(0Me)C02H Reagents i, NaH ii, NaOH-MeOH 

1 General Reactions.- Borane-1,4-thioxane hydroborated alkenes rapidly, and was used to prqKire synthetically useful monoalkyl- or dialkylboranes the 1,4-thioxane byproduct did not interfm-e with with the subsequrat utilisation of these reagents. The addition of catecholbor-ane to 2-substituted l-buten-3-ynes was catalysed by phosphine palladium(0) complexes the 

Since polysaccharides are constituted of monosaccharide units, they undergo approximately the same chemical reactions as simple sugars. How- 

Polysaccharides are capable of ester formation with either organic or inorganic acids. Reaction may, in general, be effected by any of the well-known esterification procedures after their adaptation and modification to fit the possible special requirements of carbohydrate macromolecules. The esters produced are derivatives of high polymers and as such portray typical macromolecular properties in addition to natural ester behavior. Esterification with organic acids usually alters the properties from hydrophilic to hydrophobic, and, hence, alters the solubility so that the ester is no longer soluble in water but is soluble in organic liquids. 

Commercial cellulose acetate is produced from purified cotton linters or wood pulp which are pretreated with acetic acid at a temperature less than 50 to bring about partial swelling and increased reactivity. Acetylation is accomplished with a mixture of acetic acid, acetic anhydride, and sulfuric acid (or sometimes perchloric acid). The amount of acetic anhydride 

Nitrates of both cellulose and starch can be prepared by the action of dinitrogen pentoxide on the respective polysaccharide 185,136). 

Denitration can be achieved by strong sulfuric acid, but depolymerization of the carbohydrate also occurs. Alkaline hydrolysis gives rise to a mixture of polysaccharide fragmentation products as well as inorganic nitrates and nitrites. Nitrate groups are removed without appreciable degradation 

In any reaction resulting in the formation of a chain or network of high molar mass, the functionality (see Section 1.2) of the monomer is of prime importance. In step-growth polymerization, a linear chain of monomer residues is obtained by the stepwise intermolecular condensation or addition of the reactive groups in bifunctional monomers. These reactions are analogous to simple reactions involving monofunctional units as typified by a polyesterification reaction involving a diol and a diacid. 

If the water is removed as it is formed, no equilibrium is established and the first stage in the reaction is the formation of a dimer, which is also bifunctional. As the reaction proceeds, longer chains, trimers, tetramers, and so on will form through 

Two major gronps, both distinguished by the type of monomer involved, can be identified in step-growth polymerization. In the first group, two polyfuncfional monomers take part in the reaction, and each possesses only one distinct type of functional group as in the previous esterification reaction, or more generally  

The second gronp is encoimtered when the monomer contains more than one type of fnncfional group such as a hydroxyacid (HO—R—COOH), represented generally as A-B, where the reaction is 

Other finks and groups are involved in these reactions, and some typical step-reaction polymers are shown in Table 2.1. 

Quinoxaline is resistant to nitration under mild conditions. On treatment with a mixture of oleum and nitric acid at 90°C for 24 

The nitration of 6-methoxyquinoxaline in concentrated sulfuric acid at 0°C gives 6-methoxy-5-nitroquinoxaline. The position of the nitro group is confirmed by reduction of the product to 5-amino-6-methoxy-quinoxaline identical with a sample prepared from 2,3,4-triamino-anisole and glyoxal  

Nitration of 5-niethoxyquinoxaline furnishes a dinitro derivative, presumably 5-methoxy-6,8-dinitrociuinoxaline, but no mononitro derivative could be isolated.  

The bromination of 5,8-dimethoxyquinoxaline in methanol gives a mixture of 6-bromo and 6,7-dibromo compounds/ Treatment of 2-methylquinoxaline with bromine in acetic acid yields a mixture of 27% of 2 bromomethyl- and 37% of 2-dibromomethyl-quinoxaline. Thus in the absence of powerfully activating groups, side-chain rather than nuclear substitution takes place. 

A careful study of the phenylation of quinoxaline with benzoyl peroxide, various benzenediazonium salts, and A -nitrosoacetanilide indicates that the 2-position is most reactive to phenyl radicals and that the 5-position is more reactive than the 6. The yields of 2-, 5-, and 6-phenylquinoxaline are in the ratio of 40 10 1, Benzoyl peroxide and A—nitrosoacetanilide are the most effective phenylating reagents. 

There are several compounds that will react with amino acids to give coloured or fluorescent products and as a result can be used in qualitative or quantitative methods. Fluorimetric methods are gaining in popularity and offer some important advantages over absorption spectrophotometry for amino acid analysis. 

The molar absorption coefficient of the coloured product can be used in the quantitation of individual amino acids but this value varies from one amino acid to another and must be determined under the conditions of the assay. An accepted value, however, must be used in the quantitation of the total amino acids in a mixture when absorbance readings are normally taken at 570 nm. 

Amines other than a-amino acids will also give a colour reaction with ninhydrin but without the production of carbon dioxide. Thus /3-, y-, 8- and e-amino acids and peptides react more slowly than a-amino acids, to give the blue complex, while imino acids result in the formation of a yellow-coloured product which can be measured at 440 nm. Removal of substances such as protein, ammonia and urea from biological samples may be necessary in quantitative work because they also react in a similar manner. 

The ninhydrin colour reaction has proved very useful in qualitative work and is widely used in the visualization of amino acid bands after electrophoretic or chromatographic separation of mixtures. The reagent used in such circumstances is usually prepared in ethanol and, if 2,4,6-collidine is added, the variations in colour produced by different amino acids will aid their identification (Table 10.6). 

oxidative decarboxylation of the amino acid and the production of reduced ninhydrin, ammonia and carbon dioxide  

The reduction with sodium and alcohol leads to reduction of both rings, and Armarego44 has recently shown that this method affords 

Arnold and A. Holly, Collection Czech. Chem. Commun. 28, 2040 (1963). 

The dehalogenation of naphthyridines with hydrogen over palladium on calcium carbonate in a weakly basic alcoholic solution gives excellent yields (90-95%) of reduced compounds.38,45,134,137,138 This method for removal of halogens has been extensively used and generally surpasses the classic hydrazine-copper sulfate reduction method. 

The use of other metal catalysts in attempted reductions of halo-naphthyridines has resulted in reduction of the ring or, at best, in the formation of mixtures. 

Lithium aluminum hydride (LAH) has been used139 to prepare the tetrahydro-l,7-naphthyridine (121) from either compound 120 or 122. 

Acylation (see also imder Friedel-Crafts) of enolate 

Carbony lation Carboxylation Chlorination from alcohol Cyclization 

Pit75b, Re 174, Cam71a Far76 

Na enolate Zn enolate Enol ether chemistry silyl enol ether Ester hydrolysis Free radical 

Phosphorylation Photochemical cyclization Reductions acid to alcohol DIBAL 

Scoffoni, E. Vianello, and A. Lorenzini, Gazz. chim. ital. 87, 354 (1957). 26M. Jutisz and W. Ritschard, Biochim. et Biophys. Acta 17, 548 (1955). 

2 Hirotaka Otomasu and Shoichi Nakajima, Chem. Pharm. Bull. (Tokyo) 6, 566 (1958) Chem. Abstr. 53, 10243 (1959). 

Products of addition of IF424 and of A-chlorosulphonamides425 to / -menth-l-ene, of Bra to y-terpinene,426 of NOC1 to p-menth-3-ene,427 and of hydration of a-terpineol428 have been characterized. An interesting example of remote and selective 

Menthone was elegantly transposed into carvomenthone by the sequence (196)- (197).439 Piperitol was isomerized into isomenthone over cobalt catalysts.440 Piperitone, p-menth-3-en-2-one, and 8,9-dihydrocarvone can by pyrolysed to aromatics that have lost the Pr group in fair yields (30—50%),441 and menthone can be converted into piperitone and other p-menthen-3-ones via bromination and Zn treatment.442 Pulegone on reaction with HOC1 formed 4-chloro-/ -menth-8-en-3-one,448 and O-acetylated dienolates of pulegone have been prepared.444 Carvo-menthene oxide was isomerized to p-menth-1 (7)-en-2-ol, carvotanacetol, and cyclopentane derivatives over solid acids and bases,445 and 6-thiophenoxy-8,9- 

Pancrazi, I. Kabore, B. Delpech, and Q. Khuong-Huu, Tetrahedron Lett., 1979, 3729. 

Nomura, Y. Fujihara, and Y. Matsubara, Nippon Kagaku Kaishi, 1979, 305. 

Studies using 2H-labelling have indicated that allylic alkylation of carveyl acetate catalysed by Pd° complexes involve a symmetrical 7 allyl intermediate 456 this refutes a previous mechanism.456 The chirality of (203) was established by conversion 

Kogure, M. Kumagai, S. Horiuchi, and T. Sato, J. Organometallic Chem., 1976,122, 83. 

Streith, C. Fizet, and H. Fritz, Helv. Chim. Acta, 1976, 59, 2786. 

Titanium (iv) chloride with zinc in pyridine has been found to couple ketones reductively to afford symmetrical tetrasubstituted ethenes. Unsymmetrical alkenes can be synthesized in useful yields by titanium-induced ketone coupling if the less reactive component is used in excess. Cycloalkenes (ring size 4—16) are prepared in good yield by intramolecular coupling of the corresponding alkanedione.  

2(Me2N)3P + BrCCl3 - (Me2N)3P=CCl2 + (Me3N)3PBrCl  

S-Alkenyl-9-borabicyclo[3,3,l]nonanes add across the carbonyl group of simple aldehydes to give allylic alcohols after hydrolysis. The configuration of the alkene unit is retained. This mild Grignard type reaction should be compatible with many functional groups, e.g. ester, nitrile. 

The relative reactivities of different alkenes towards 9-borabicyclo[3,3,l]nonane (9-BBN) and di-isoamylborane have been studied. Di-isoamylborane is the more selective for cycloalkenes, the relative rates of hydroboration of cyclop entene, cyclo-heptene, and cis-cyclo-octene being 1.0 18.6 68.6, respectively. Hydroboration of substituted cyclo-octenes using diborane is complicated by rapid isomerization of the initially formed alkyl-borane, leading to mixtures of alcohols on oxidation. However, 9-alkyl-9-borabicyclo[3,3,l]nonanes are thermally stable, and hydroboronation of 1-alkylcyclo-octenes using 9-BBN leads sp ecifically to trans-2-alkylcyclo-octanols after oxidation.  

The relative rate constants for the reduction of a range of cyclic alkenes by di-imide have been determined the results agree qualitatively with those reported earlier/ The effect of ring size on the rate of hydrogenation of 2-benzylidenecycloalkanols has been examined hydrogen addition usually occurs cis- to the hydroxy-group.  

Cyclopropane derivatives have been prepared using alkenes, cm-dihalides, and copper. This is a convenient and useful procedure, e.g. cis-cyclo-octene was converted into bicyclo[6,l,0]nonane (77%) and into a mixture of endo- and cxo-9-methoxy-carbonylbicyclo[6,l,0]nonanes (71 % exo. endo = 1.3 1) using di-iodomethane and methyl dibromoacetate, respectively. An improved procedure for the conversion of alkenes into cyclopropanols uses lithium 2,2,6,6-tetramethylpiperidide and 2-chloroethyl chloromethyl ether, e.g. cycloheptene was converted into the 2-chloro-ethyl ether of bicyclo[5,l,0]octan-8-ol (62% exo.endo = 1.8 1).  

The rate of lithium aluminium hydride reduction of epoxycycloalkanes in diethyl ether diminishes slowly from C5 to C- drops sharply for Cg, reaches a minimum for Cio and increases up to Cjg. In all cases the cis-epoxide is reduced faster than the trans.  

Cycloalkanes.—Rates of hydrogen abstraction from cycloheptane and cyclooctane by the p-nitrophenyl radical, and the autoxidation of phenyl-cycloheptane and -cyclo-octane are discussed.  

Various physical properties are reported for cycloheptane and cyclo-octane.  

Cycloalkenes.—One-step acyloxylation of a variety of cyclic olefins using t-butyl peroxyacetate and t-butyl peroxybenzoate is reviewed.  

Relative reactivities have been determined for the free-radical addition of 1-iodoperfluoropropane to olefins, including cycloheptene and cyclo-octene the latter gives transannular as well as 1,2-products. Rates of transoxy- 

An improved procedure is reported for the oxidation of olefins to cis-1,2-diols, involving oxidation by potassium permanganate in aqueous sodium hydroxide-methylene chloride in the presence of triethylbenzylammonium chloride in this way cyclo-octene gave cyclo-octane-1,2-diol (50%). Lower yields were obtained when the glycol was highly soluble in the aqueous phase. 

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For general reactions see olefins. The butylenes are used to prepare 2-butanol. I-Butene and isobutene are formed into widely used polymers. 

For gas reactions where the gases are assumed to follow ideal behaviour this equation becomes AG° = RT]n Kp, where Kp is defined in terms of the partial pressures of reactants and products. Thus for the general reaction above,... 

For a more general reaction of the fonn Ox + ne Red, with differing concentrations of Ox and Red, the exchange current density is given by... 

Vibrational motion is thus an important primary step in a general reaction mechanism and detailed investigation of this motion is of utmost relevance for our understanding of the dynamics of chemical reactions. In classical mechanics, vibrational motion is described by the time evolution and l t) of general internal position and momentum coordinates. These time dependent fiinctions are solutions of the classical equations of motion, e.g. Newton s equations for given initial conditions and I Iq) = Pq. 

A general reaction scheme for CIDNP is shown in llgnre B1.16.4B. where the radical dynamics in each region... 

The general characteristics of all these elements generally preclude their extraction by any method involving aqueous solution. For the lighter, less volatile metals (Li, Na, Be, Mg, Ca) electrolysis of a fused salt (usually the chloride), or of a mixture of salts, is used. The heavier, more volatile metals in each group can all be similarly obtained by electrolysis, but it is usually more convenient to take advantage of their volatility and obtain them from their oxides or chlorides by displacement, i.e. by general reactions such as... 

The replacement of the —OH group by a chlorine atom (reaction 9.4) is a very general reaction of phosphorus pentachloride. For example, if concentrated sulphuric acid is written as (H0)2S02 then its reaction with phosphorus pentachloride may be written ... 

Reactions can be considered as composite systems containing reactant and product molecules, as well as reaction sites. The similarity of chemical structures is defined by generalized reaction types and by gross structural features. The similarity of reactions can be defined by physicochemical parameters of the atoms and bonds at the reaction site. These definitions provide criteria for searching reaction databases [23],... 

In eachof the Sections 10-27, the chief physical propertiesof the compounds concerned are Erst briefly indicated a list of the gen eral reactionsf is then given, followed by practical directions for the application or illustration of these general reactions. The types of crystalline derivatives which can be most readily and reliably prepared are then given, with practical examples. Finally, any important special reactions of individual members are described. 

Urethanes. The reaction with phenylisocyanate should be used for crystalline derivative formation (see below), and not as a general reaction for alcohols. 

In addition to General Reactions i and 2, all amides react with nitrous acid evolving nitrogen ... 

D) No general reaction can be cited for the preparation of crystalline derivatives of Class (iii). Triphenylamine, when nitrated in acetic acid with fuming nitric acid, gives tri-/>-nitrophenylamine, m.p. 280°. The presence of substituents in the phenyl groups may however complicate or invalidate nitration. 

Nitroethane may be similarly obtained from sodium a chloropropionate. This is a general reaction for a chloro carboxylic acids, but in practice only monochloroacetic acid and a chloropropionic acid are readily available. 

The student should carry out the following simple experiments with acetamide or with any other ahphatic amide, e.g., n-caproamide they illustrate some of the general reactions of primary ahphatic amides. 

The formation of ethyl acetoacetate is an example of a general reaction knowu as the acetoacetlc ester condensation in which an ester having hydrogen on the a-carbon atom condenses with a second molecule of the same ester or with another ester (which may or may not have hydrogen on the a-carbon atom) in the presence of a basic catalyst (sodium, sodium ethoxide, sodamide, sodium triphenylmethide) to form a p-keto-ester. The mechanism of the reaction may be illustrated by the condensation of ethyl acetate with another molecule of ethyl acetate by means of sodium ethoxide. ... 

The acetoacetic ester condensation (involving the acylation of an ester by an ester) is a special case of a more general reaction term the Claisen condensation. The latter is the condensation between a carboxylic ester and an ester (or ketone or nitrile) containing an a-hydrogen atom in the presence of a base (sodium, sodium alkoxide, sodamide, sodium triphenylmethide, etc.). If R—H is the compound containing the a- or active hydrogen atom, the Claisen condensation may be written ... 

The precipitated amine hydrochloride (or sulphate), if any, dissolves during the diazotisation to give a clear solution of the highly soluble diazonium salt. The general reaction may be written ... 

The above appears to be a general reaction for converting a-hydroxy ketones into diketones in excellent yield thus furoin and anisoin give furil and anisil respectively. The reaction is probably ... 

Section IV, 135,5), but are unaflFected by the dimedone reagent (Section 111,70, 2). The general reactions are similar to those already given under Aliphatic Ketones (Section 111,74). Owing to their higher molecular weight, such derivatives as oximes and phenylhydrazones are frequently quite satisfactory. 

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