Aldehyde condensation structures

In the first century of "organic" chemistry much attention was given to the structures of carbogens and their transformations. Reactions were classified according to the types of substrates that underwent the chemical change (for example "aromatic substitution," "carbonyl addition," "halide displacement," "ester condensation"). Chemistry was taught and learned as transformations characteristic of a structural class (e.g. phenol, aldehyde) or structural subunit... 

Draw a condensed structural diagram for each aldehyde or ketone. 

Molecular self-assembly will not be considered here (see [9.2]) in fact, it is a special type of synthetic procedure where several reactions between several reagents occur in one experimental operation to yield the final covalent structure it is subject to control by the intramolecular conformational features of intermediates and by the stereochemistry of the reaction(s) the efficient assembly of a covalent structure may require that the connecting reaction(s) be reversible so as to allow searching for the final structure. Examples are found in the generation of macropolycyclic structures by multiple (amine-aldehyde) condensations (see Section 4.1) or of porphyrinogens, porphyrins and phthalocyanins (see also in [9.13a]. 

When a condensed structural formula is written for a compound containing double or triple bonds, the multiple bonds are often drawn as they would be in a Lewis structure. Table 1-3 shows examples of condensed structural formulas containing multiple bonds. Notice that the —CHO group of an aldehyde and the —COOH group of a carboxylic acid are actually bonded differently from what the condensed notation suggests. Condensed structures are assumed to follow the octet rule even if the condensed notation does not show the bonding. 

The synthesis of methyl ketone 281 began with the reaction between the tetra-substituted allylborane 279 and 2,3-0-isopropylidene-D-glyceraldehyde 48. The resulting homoallylic alcohol 280, obtained in 73% yield and excellent selectivity (exact ratio not defined) [231], was converted in two steps to the methyl ketone 281. Aldol condensation between the lithium enolate of 281 and aldehyde 278 (structure shown in Scheme 11-12) gave, after protection of the initial adduct, the Felkin diastereomer 282 as the only reported product in 54% yield. This adduct... 

Resorcinarenes are synthesized by condensation of resorcine and aldehydes.The structures of calix- and resorcinarenes are similar, the compounds differing only with respect to the number and position of substituents [51]. Since formaldehyde can be replaced by other aldehydes, the bridging methylene groups can be modified in the condensation reaction (Fig. 10.4) [52].This approach may be suitable for the parallel synthesis of more diverse recognition sites. 

Write condensed structural formulas for the two aldehydes with the molecular formula C4H8O. 

Structural acrylic chemistry is very similar to anaerobic chemistry. The differences arise in the reactions that take place to initiate polymerization. The common initiator/curative redox couple in structural acrylic technology, hydroperoxide/amine-aldehyde condensate, reacts to generate alkoxy radicals. The exact fate of the DHP in the redox reaction is not known. However, a likely first step involves hydrogen abstraction as shown in Eq. (7). 

For several experimental and computational investigatioiis on similar reactions, see (a) M. N. Paddon-Row, N. G. Rondan, K. N. Houk, J. Am. Chem. Soc. 1982, 104, 7162—7166. Staggered models for asymmetric induction attack trajectories and conformations of allylic bonds from ab initio transition structures of addition reactions, (b) S. E. Denmark, E. J. Weber, Helv. Chim. Acta 1983, 159, 1655-1660. On the stereochemistry of aUyl-metal-aldehyde condensations, (c) S. E. Denmark, E. J. Weber,... 

The calixarenes (from the Greek calix, meaning chalice) are a family of structures that have seen extensive use in many contexts. Shown below is the remarkable, one-step synthesis of the prototype calixarene. This condensation reaction is a variant of the phenol-aldehyde condensation that produces bakelite, the first synthetic polymer. Early workers spent considerable effort to optimize this synthesis, biasing the product toward the calixarene... 

FIGURE 14.27 A flow chart emphasizing the aldehyde classification and giving the condensed structures and lUPAC names (left) and common names (right) of two simple aldehydes. 

Draw the condensed structural formula for the aldehyde or ketone formed by the oxidation of each of the following ... 

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