B Aldehydes and ketones

The carbonyl group in a perfluorinated ketone is clearly very electron-deficient and this feature dominates the chemistry of these compounds. It is reflected in, for example, the rise in vibrational frequency of the carbonyl group in polyfluoro-ketones [97, 98] from normal values and by the fact that hexafluoroacetone is not protonated in the superacidic FS03H/Sbp5 mixture [8]. 

A significant feature in this chemistry is the presence of low-lying HOMOs in the heterodienes this has made possible a range of cycloaddition reactions [95, 96] 

Copolymers are obtained by free-radical copolymerisation of hexafluoroacetone with, for example, alkenes, tetrafluoroethene and epoxides. 

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Ans. (a) Aldehydes, ketones, acids, amides, and esters (b) Aldehydes and ketones... 

CHAPTER 19 B Aldehydes and Ketones Nucleophilic Addition Reactions... 

Phenylhydrazones (compare Section III,74,C). Dissolve 0-5 g, of colourless phenylhydrazine hydrochloride and 0 8 g. of sodium acetate in 5 ml. of water, and add a solution of 0-2-0-4 g. of the aldehyde (or ketone) in a little alcohol (free from aldehydes and ketones). Shake the mixture until a clear solution is obtained and add a little more alcohol, if necessary. Warm on a water bath for 10-15 minutes and cool. Filter ofiF the crystalline derivative, and recrystalhse it from dilute alcohol or water sometimes benzene or light petroleum (b.p. 60-80°) may be used. 

The production of both an alcohol and the sodium salt of an acid might easily be confused with the hydrolysis products of an ester (in the above instance benzyl benzoate). Such an error would soon be discovered (e.g., by reference to the b.p. and other physical properties), but it would lead to an unnecessary expenditure of time and energy. The above example, however, emphasises the importance of conducting the class reactions of neutral oxygen-containing compounds in the proper order, viz., (1) aldehydes and ketones, (2) esters and anhydrides, (3) alcohols, and (4) ethers. 

Like other alkaloids of this group, quinine forms molecular compounds with a variety of organic substances. With benzene and toluene it produces compounds of the formulae B. CgHg and B. C,Hg respectively, with phenol it gives the crystalline product B. CgHjOH, and similar combinations with polyhydric phenols, ethers, aldehydes and ketones are known. One of the most characteristic of these substances is cupreine-quinine, a combination of the two alkaloids, obtainable from cuprea bark, and at first regarded as a new alkaloid, and named homoquinine. ... 

Reaction of ketones such as 1-menthone 398 with silylated glycolic acid 417 in the presence of catalytic amounts of TMSOTf 20 provides an lil-mixture of the l,3-dioxolan-4-ones 418 and 419 [35, 36]. Likewise, other aldehydes and ketones [37, 38] and pivaldehyde [39] react with substituted silylated glycohc adds 420 a, b and yS-hydroxy acids 420c to give, e.g., 421 a, b and 421c as mixtures [37-40]. Reaction of pivaldehyde with the persilylated hydroxy acid 420 d and TMSOTf 20 to... 

It is convenient to consider the indifferent or neutral oxygen derivatives of the hydrocarbons—(a) aldehydes and ketones, (b) esters and anhydrides, (c) alcohols and ethers— together. All of these, with the exception of the water-soluble members of low molecular weight, are soluble only in concentrated sulphuric acid, t.e., fall into Solubility Group V. The above classes of compounds must be tested for in the order in which they are listed, otherwise erroneous conclusions may be drawn from the reactions for functional groups about to be described. 

Which of these two groups provide the bonding sites when the two amino acids shown above combine A Carboxyl and hydrogen B Aldehyde and amino C Ketone and amino D Amino and carboxyl... 

B. Reactions with aldehydes and ketones to give alcohols... 

Allylic boranes such as 9-allyl-9-BBN react with aldehydes and ketones to give allylic carbinols. The reaction begins by Lewis acid-base coordination at the carbonyl oxygen, which both increases the electrophilicity of the carbonyl group and weakens the C-B bond to the allyl group. The dipolar adduct then reacts through a cyclic TS. Bond formation takes place at the 7-carbon of the allyl group and the double bond shifts.36 After the reaction is complete, the carbinol product is liberated from the borinate ester by displacement with ethanolamine. Yields for a series of aldehydes and ketones were usually above 90% for 9-allyl-9-BBN. 

In addition to reactions at the Zn-C bond, the complexes [BpBut]ZnR also exhibit reactivity at the B-H bond. Thus, [BpBu ]ZnR reacts with aldehydes and ketones, (CH20) , MeCHO, and Me2CO, to give HB(OR )(3-Butpz)2 ZnR (R = Me, Et, Pr1), as a result of insertion into the B-H bond. In contrast, the tris(pyrazolyl)hydroborato complexes [TpBut]ZnR are inert towards B-H insertion under similar conditions. 

The reactions of a-bromoalkyl nitrones (298) with secondary amines lead initially to a-dialkylamino derivatives (432), which on heating, give aldehydes and ketones (75a,b) in high yield (Scheme 2.205) (540). 

Concerted acid-base catalysed enolizations of a range of simple aldehydes and ketones have been measured in water at 25 °C, using a range of substituted acetic acid-acetate buffers.The buffer plots yield rate constants for acid (A a) and base ( b) catalytic terms in the normal way at low buffer concentrations. Extension up to higher concentrations (as far as [total buffer] = 2 m, typically) yields the third-order term ( ab) via upward curvature of the plots. While ab does not have a simple correlation with either k or b, it does correlate with their product, i.e. 

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