Compounds, addition

A large amount of work has been done on exchange involving addition compounds of Group III alkyl derivatives, but before treating these it would be useful to discuss studies carried out on BF3 adducts since these studies lay the groundwork for most of the later discussion. 

In systems containing BF3 and two ethers, two routes for exchange have been proposed (119-121). The first of these, predominating in solutions containing a large excess of uncomplexed ether, is a nucleophilic displacement described by Eq. (31). 

In solutions containing little or no free ether, a different bimolecular exchange appears to be operative  

Diehl (35, 36) has observed the exchange reactions in BF3-alcohol systems by l9F resonance. The exchange in these systems, where the ratio of BF3 to alcohol is less than one, was attributed to the exchange of alcohol in a hydrogen bonded dicomplex with structure (XIII). 

The activation energy of 7.3 kcal/mole remains constant for several concentration ratios, but the concentration dependence of the lifetime of the complex species shows a sharp change in value at BF3/ROH 0.5. This can probably be explained by the fact that the dicomplex above is a completely solvated form of the BF3-ROH complex. When BF3/ROH 0.5, Eq. (33) will describe the exchange (43). 

The product is the disodium salt of 1,4-tetraphenylbutane (which is formed on adding water) and could thus be regarded as a substitution compound, but is commonly classified as a product of the dimerizing addition of sodium to an olefin. Another example of dimerizing addition (though 

Hydrolysis yields 1,2,3,4-tetraphenylbutadiene, but reaction with some dihalides has allowed some interesting heterocyclic syntheses, e.g. a highly reactive potentially antiaromatic borole. 

The other kind of addition compound, exemplified by sodium-naphthalene, cannot be regarded as a substitution product, as it is formed by the addition of one or more electrons to the lowest vacant molecular orbital of an aromatic hydrocarbon. Aromatic hydrocarbons containing two or more aromatic rings, joined (biphenyl, terphenyls), conjugated (1,4-diphenylbutadiene), or fused (naphthalene, anthracene), react with alkali metal without loss of hydrogen. Tliese addition compounds are all strongly coloured, and their formation is greatly facilitated in basic solvents such as tetrahydrofuran or 1,2-dimethoxyethane. 

Solutions of sodium-naphthalene in tetrahydrofuran are dark green, electrically conducting because the compound is a salt Na (THF) CioHs , and paramagnetic because of the extra electron which is in a singly occupied 7r-orbital. Information about the distribution of the unpaired electron about its various possible positions in the anion can in suitable cases be derived from the electron spin resonance spectrum. If the orbital occupied by the unpaired electron in a hydrocarbon anion is non-degenerate, as is the case with naphthalene and anthracene, then a second electron (formation of anion ) would enter the same orbital and both the paramagnetism and e.s.r. spectra disappear. 

Aromatic hydrocarbons vary considerably in their electron afiSnities, e.g. benzene biphenyl naphthalene phenanthrene pyrene anthracene. Addition of sodium-biphenyl, for example, to a solution of a hydrocarbon of greater electron afiSnity results in electron transfer, frequently accompanied by a colour change  

OH group in the same molecule.34 Another type of molecule in which carbon is the B 

Deuterium also forms hydrogen bonds in some systems these seem to be stronger than the corresponding hydrogen bonds in others, weaker.39 

When the reaction of two compounds results in a product that contains all the mass of the two compounds, the product is called an addition compound. There are several kinds. In the rest of this chapter we will discuss addition compounds in which the molecules of the starting materials remain more or less intact and weak bonds hold two or more molecules together. We can divide them into four broad classes electron donor-acceptor complexes, complexes formed by crown ethers and similar compounds, inclusion compounds, and catenanes. 

In EDA complexes,41 there is always a donor molecule and an acceptor. The donor may donate an unshared pair (an n donor) or a pair of electrons in a it orbital of a double bond or aromatic system (a u donor). One test for the presence of an EDA complex is the electronic spectrum. These complexes generally exhibit a spectrum (called a charge-transfer 

Complexes in which the acceptor is a metal ion and the donor an olefin or an aromatic ring (n donors do not give EDA complexes with metal ions but form covalent bonds instead).41 Many metal ions form complexes, which are often stable solids, with olefins, dienes (usually conjugated, but not always), alkynes, and aromatic rings. The generally accepted picture of the bonding in these complexes,44 first proposed by Dewar,45 can be illustrated for the complex in which silver ion is bonded to an olefin. There are two bonds between the metal ion and the olefin. One is a a bond formed by overlap of the filled -it orbital of the olefin with the empty 5s orbital of the silver ion, and the other a -it bond 

The complex dichlorodiammineplatinum(II), Cl2Pt(NH3)2, has a planar configuration. Two forms are known  

Two groups are said to be in the trans positions when the line connecting them passes through the center of coordination. Otherwise they are in cis positions. As is seen, in the cis form of the above complex, both the two chlorines and the two ammonias occupy positions cis to each other. Similar designations may be applied to octahedral complexes. 

The terms hydrate, ammoniate, alcoholate, and etherate have long been used by chemists in referring to addition compounds. It seems preferable, however, when such compounds may be appropriately regarded as coordination compounds to refer to them as such  

The names given are more explicit than iron(III) nitrate hexahydrate or cobalt(III) chloride hexaammoniate. In assigning names of this sort, it is thus important to know something about the structure of the compound or be at least able to make intelligent guesses as to it. Naming 

Finally it should be noted that although one might not find a compound listed uhder an incorrect name, there is no guarantee that it will be listed under its correct name either. In consulting a journal index for information about a compound, one may often save time by selecting what appears to be the most important element in the compound and looking under the section devoted to that element. Thus each of the octahedral cobalt complexes pictured above would be likely to be listed under Cobalt Compounds, whereas the two platinum complexes might very well be listed under Platinum Compounds.  

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The data base contains provisions for a simple augmentation by up to eight additional compounds or substitution of other compounds for those included. Binary interaction parameters necessary for calculation of fugacities in liquid mixtures are presently available for 180 pairs. 

CCls CHO. A colourless oily liquid with a pungent odour b.p. 98°C. Manut actured by the action of chlorine on ethanol it is also made by the chlorination of ethanal. When allowed to stand, it changes slowly to a white solid. Addition compounds are formed with water see chloral hydrate), ammonia, sodium hydrogen sulphite, alcohols, and some amines and amides. Oxidized by nitric acid to tri-chloroethanoic acid. Decomposed by alkalis to chloroform and a methanoate a convenient method of obtaining pure CHCI3. It is used for the manufacture of DDT. It is also used as a hypnotic. 

In each case the configuration around the boron changes from trigonal planar to tetrahedral on adduct formation. Because of this ability to form additional compounds, boron trifluoride is an important catalyst and is used in many organic reactions, notably polymerisation, esterification, and Friedel-Crafts acylation and alkylations. 

Carbon monoxide forms addition compounds. With chlorine in sunlight or in the presence of charcoal in the dark, carbonyl chloride... 

JiVith ammoniacal or hydrochloric acid solution of copper(I) chloride, carbon monoxide forms the addition compound CuCl. CO. 2H2O. This reaction can be used to quantitatively remove carbon monoxide from gaseous mixtures. 

Addition compounds called ozonides are produced when alkenes react with ozone and reductive cleavage of these compounds is used extensively in preparative and diagnostic organic chemistry. 

Sodium hydrogensulphite, when freshly prepared, reacts with aldehydes to form crystalline addition compounds, for example... 

Iron(III) chloride forms numerous addition compounds, especially with organic molecules which contain donor atoms, for example ethers, alcohols, aldehydes, ketones and amines. Anhydrous iron(III) chloride is soluble in, for example, ether, and can be extracted into this solvent from water the extraction is more effective in presence of chloride ion. Of other iron(III) halides, iron(III) bromide and iron(III) iodide decompose rather readily into the +2 halide and halogen. 

The solid readily dissolves chemically in concentrated hydrochloric acid, forming a complex, and in ammonia as the colourless, linear, complex cation [H3N -> Cu <- NHj] (cf AgCl) if air is absent (in the presence of air, this is oxidis to a blue ammino-copper(II) complex). This solution of ammoniacal copper(I) chloride is a good solvent or carbon monoxide, forming an addition compound CuCl. CO. H2O, and as such is used in gas analysis. On passing ethyne through the ammoniacal solution, a red-brown precipitate of hydrated copper(I) dicarbide (explosive when dry) is obtained ... 

At ordinary temperatures, zinc forms an addition compound with an alkyl halide (cf magnesium) ... 

To seat ch for available starting materials, similarity searches, substructure searches, and some classical retrieval methods such as full structure searches, name searches, empirical formula searches, etc., have been integrated into the system. All searches can be applied to a number of catalogs of available fine chemicals (c.g, Fluka 154]. In addition, compound libraries such as in-housc catalogs can easily be integrated. 

The student should note that ketones in class (1), t.c., those having the >CO group in the side chain, will form additive compounds with sodium bisulphite only if this >CO group is not directly joined to the benzene ring acetophenone therefore will not form such compounds, whereas benzyl methyl ketone, CaHsCHjCOCH, will do so. Many quinones, particularly ortho quinones such as phenanthraquinone, form additive compounds with sodium bisulphite. 

Usually form bisulphite addition compounds, R CH(0H)S03Na. 

Bisulphite addition compound. Shake 1 ml. of benzaldehyde with about 0 5 ml. of saturated NaHSOj solution. The mixture becomes warm, and the white addition product separates (rapidly on cooling). 

Bisulphite addition compound. The formation of the bisulphite compound is delayed and appears only after 2-3 minutes shaking. 

Certain ketones give bisulphite addition compounds. 

Pure pyridine may be prepared from technical coal-tar pyridine in the following manner. The technical pyridine is first dried over solid sodium hydroxide, distilled through an efficient fractionating column, and the fraction, b.p. 114 116° collected. Four hundred ml. of the redistilled p)rridine are added to a reagent prepared by dissolving 340 g. of anhydrous zinc chloride in a mixture of 210 ml. of concentrated hydrochloric acid and 1 litre of absolute ethyl alcohol. A crystalline precipitate of an addition compound (probable composition 2C5H5N,ZnCl2,HCl ) separates and some heat is evolved. When cold, this is collected by suction filtration and washed with a little absolute ethyl alcohol. The yield is about 680 g. It is recrystaUised from absolute ethyl alcohol to a constant m.p. (151-8°). The base is liberated by the addition of excess of concentrated... 

Treat a small quantity of the bisulphite addition compound with 5 ml. of 10 per cent, sodium carbonate solution, and note the odour. Repeat the experiment with 5 ml. of dilute hydrochloric acid. 

Mandelic acid. This preparation is an example of the synthesis of an a-hydroxy acid by the cyanohydrin method. To avoid the use of the very volatile and extremely poisonous hquid hydrogen cyanide, the cyanohydrin (mandelonitrile) is prepared by treatment of the so um bisulphite addition compound of benzaldehj de (not isolated) with sodium cyanide ... 

The alcohol may be purified by conversion into the calcium chloride addition compound. Treat it with anhydrous calcium chloride much heat is evolved and the addition compound is formed. After several hours, remove any oil which has not reacted by washing with petroleum ether (b.p. 60-80°). Decompose the solid with ice water, separate the alcohol, dry and distil. 

Bisulphite compounds of aldehydes and ketones. These substances are decomposed by dilute acids into the corresponding aldehydes or ketones with the liberation of sulphur dioxide. The aldehyde or ketone may be isolated by steam distillation or by extraction with ether. Owing to the highly reactive character of aldehydes, the bisulphite addition compounds are best decomposed with saturated sodium bicarbonate solution so um carbonate solution is generally employed for the bisulphite compounds of ketones. 

The soiution is aliowed to cool and the crystals of the P2P-bisulfite addition compound are then separated by vacuum filtration, washed with a little clean dH20 then washed with a couple hundred mLs of ether, DCM or benzene. The filter cake of MD-P2P-bisulfate is processed by scraping the crystals into a flask and then 300mL of either 20% sodium carbonate solution or 10% HCi soiution are added (HCI works best). The soiution is stirred for another 30 minutes during which time the MD-P2P-bisulfite complex will be busted up and the P2P will return to its happy oil form. The P2P is then taken up with ether, dried and removed of the solvent to give pure MD-P2P. Whaddya think of that ... 

In 1882, Will (90), by reacting CS2 with the product (56) resulting from the condensation of dibromoethane with N,N -diphenylthiourea, obtained the first derivative of thiazolidine-2-thione (57). He observed the reaction of 57 with methyl iodide to afford an addition compound (58). 

Alkylthiazoles react with ethylmagnesium bromide to give thiazolyl-magnesiurn compounds, as demonstrated for 4- and 5-methyithiazoles, 4-ethylthiazole. and 4,5-dimethylthiazole. The resulting addition compounds do not decompose at high temperature and pressure to yield alkylthiazoles as do the addition compounds obtained with pyridine. 

Use of Centered Period. A centered period is used to denote water of hydration, other solvates, and addition compounds for example, CUSO4 SHjO, copper(II) sulfate 5-water (or pen-tahydrate). 

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