Hahdes

Wurtz - Fittig reaction. The interaction of an aryl halide, alkyl hahde and sodium gives a reasonable yield of an alkyl aryl hydrocarbon, for example ... 

The use of dimethylformamide (b.p. 153°) as a solvent and diluent often increases the yield materially. The vigour of the exothermic reaction which occurs with a relatively reactive aryl hahde is moderated and, furthermore, the dimethylformamide is easily removed from the reaction product since it is water soluble. Aryl hahdes which are inert under the usual Ullmann conditions do not react in the presence of dimethylformamide. 

Reaction with chlorosulphonic acid ( chlorosulphonyl-ation ). Sulphonamides. Many aryl hahdes, either alone or in chloroform solution, when treated with excess of chlorosulphonic acid afford the corresponding sulphonyl chlorides in good yield (compare Section IV.106) the latter may be readily converted into the aryl sulphonamides by reaction with concentrated ammonia solution or with sohd ammonium carbonate. 

Acyl hahdes may be identified by —hydrolysis to the corresponding acids (the latter may be further characterised as in Section IV,175) conversion into amides (Section IV,191), anihdes or p-toluidides (Section IV,100) and conversion into sohd esters (Section IV,183). 

Alternatively, add 1 or 2 drops of 5 per cent, nickel nitrate solution to 2-3 ml. of the fusion solution, filter off the nickel cyanide and/or nickel sulphide, acidify the filtrate with 2N nitric acid, and test for hahdes as above. 

When an organic compound is heated with a mixture of zinc powder and sodium carbonate, the nitrogen and halogens are converted into sodium cyanide and sodium hahdes respectively, and the sulphur into zinc sulphide (insoluble in water). The sodium cyanide and sodium hahdes are extracted with water and detected as in Lassaigne s method, whilst the zinc sulphide in the residue is decomposed with dilute acid and the hydrogen sulphide is identified with sodium plumbite or lead acetate paper. The test for nitrogen is thus not affected by the presence of sulphur this constitutes an advantage of the method. 

This time the one-carbon discoimection a is all right because the Grignard reagent is Ifom a normal alkyl hahde and does not polymerise. 

Another similar example concerns the alkylation of enamines. This reaction works well with reactive a-halocarbonyl compounds (frames 175ff) but simple alkyl hahdes often react on nitrogen ... 

Strategy Problem 1 The wrong substitution pattern . Making aromatic compounds m-substituted with two o -directing groups is always a problem. What strategies can you suggest An example (TM 412) is the alkyl hahde used in the synthesis of some steroids. 

Partial but not complete loss of optical activity m S l reactions probably results from the carbocation not being completely free when it is attacked by the nucleophile Ionization of the alkyl halide gives a carbocation-hahde ion pair as depicted m Figure 8 8 The halide ion shields one side of the carbocation and the nucleophile captures the carbocation faster from the opposite side More product of inverted configuration is formed than product of retained configuration In spite of the observation that the products of S l reactions are only partially racemic the fact that these reactions are not stereospecific is more consistent with a carbocation intermediate than a concerted bimolecular mechanism... 

Dry-Film Resists Based on Radical Photopolymerization. Photoinitiated polymerization (PIP) is widely practiced ia bulk systems, but special measures must be taken to apply the chemistry ia Hthographic appHcations. The attractive aspect of PIP is that each initiator species produced by photolysis launches a cascade of chemical events, effectively forming multiple chemical bonds for each photon absorbed. The gain that results constitutes a form of "chemical amplification" analogous to that observed ia silver hahde photography, and illustrates a path for achieving very high photosensitivities. 

Nitdles may be prepared by several methods (1). The first nitrile to be prepared was propionitdle, which was obtained in 1834 by distilling barium ethyl sulfate with potassium cyanide. This is a general preparation of nitriles from sulfonate salts and is referred to as the Pelou2e reaction (2). Although not commonly practiced today, dehydration of amides has been widely used to produce nitriles and was the first commercial synthesis of a nitrile. The reaction of alkyl hahdes with sodium cyanide to produce nitriles (eq. 1) also is a general reaction with wide appHcabiUty ... 

Complexes of DMAC and many inorganic haHdes have been reported (20). These complexes are of iaterest because they catalyze a number of organic reactions. Complexes of DMAC and such heavy metal salts as NiBr2 exert a greater catalytic activity than the simple salts (21). The crystalline complex of SO and dimethylacetamide has been suggested for moderating the reaction conditions ia sulfation of leuco vat dyestuffs (22). 

With two equivalents of an organomagnesium hahde, a Gtignard reagent is formed, capable of use in further syntheses (35,36). Cuprous salts cataly2e oxidative dimerization of propargyl alcohol to 2,4-hexadiyne-l,6-diol [3031-68-3] (37). 

Although stable at ambieat temperature, calcium fluoride is slowly hydrolyzed by moist air at about 1200°C, presumably to CaO and HF. Calcium fluoride is not attacked by alkahes or by reactive fluorine compounds, but is decomposed by hot, high boiling acids, as ia the reactioa with coaceatrated sulfuric acid which is the process used to produce hydrogea fluoride. Calcium fluoride is slightly soluble ia cold dilute acids, and somewhat more soluble ia solutioas of alumiaum hahdes. 

Volatile impurities, eg, F2, HF, CIF, and CI2, in halogen fluoride compounds are most easily deterrnined by gas chromatography (109—111). The use of Ftoroplast adsorbents to determine certain volatile impurities to a detection limit of 0.01% has been described (112—114). Free halogen and haHde concentrations can be deterrnined by wet chemical analysis of hydrolyzed halogen fluoride compounds. 

K [14881-07-3], Rb [72151 -96-3], and Cs [72138-72-8]), are prepared by reaction of elemental fluorine, chlorine trifluoride, or xenon difluoride and a mixture of nickel fluoride and alkaH metal fluorides or other metal haHdes (16,17). If the fluorination is carried out using mixed fluorides, a lower temperature can be used, yields are quantitative, and the final products are of high purity. Bis(tetrafluoroammonium) hexafluoronickelate [6310540-8], (NE 2N iF6> prepared from Cs2NiF3 and NE SbE by a metathesis in anhydrous HE, is also known (18). 

The most promising appHcation of titanium tetrafluoride is for use in topical appHcations for prevention of dental caries (7—13). It is being evaluated and compared to NaF, MFP, and SnF2 used in these appHcations. The other use is in mixed optical haHde glass (14—16), and in the preparation of fluorotitanates (17—19). 

Aromatic perfluoroaLkylation can be effected by fluorinated aUphatics via different techniques. One category features copper-assisted coupling of aryl hahdes with perfluoroalkyl iodides (eg, CF I) (111,112) or difluoromethane derivatives such as CF2Br2 (Burton s reagent) (113,114), as well as electrochemical trifluoromethylation using CF Br with a sacrificial copper anode (115). Extmsion of spacer groups attached to the fluoroalkyl moiety, eg,... 

Acidic hahde catalysts used in chloromethylation include (44) ZnCl, ZnCl2 + AlCl, SnCl, SnCl, AlCl +ketones, AlCl + pyridine, AlCl ... 

Arylation of Aromatic Compounds. In contrast to Friedel-Crafts alkylations, arylations of aromatics are not as well known, and usually require drastic conditions. They iaclude (/) dehydrogenating condensation (SchoU reaction) (2) arylation with aryl haUdes and (J) arylation with dia2onium hahdes. 

Olefins and cycloolefins give unsaturated ketones with acyl hahdes (the Nenitzescu reaction) (170). Saturated chloroketones are formed as intermediates followed by elimination of HCl. Similar products may be obtained by using acid... 

Gallium (I). Hahdes of Ga(I) ate known only in the vapor phase. Coordination complexes of GaCl and GaBt have been obtained with dioxane, morpholine, and acetylacetone. 

---