Megaphone

Megaphones, synthesis of 1250, 1252 Mercaptocalix[4]arenes, synthesis of 1402 [l.l.l.l]Metacyclophane framework 322 [l ]Metacyclophanes 1370 Metalation, directed 677 Metathesis reactions 1432 trarw-3-Methoxy-4-hydroxycinnamic acid, as MALDl matrix 323 Methoxylation 1167... 

The dAc dz term is usually zero since most tubular reactors have a constant diameter. For the exceptional case, we suppose that Adz) is known, say from the design drawings of the reactor. It must be a smooth (meaning differentiable) and slowly varying function of z or else the assumption of piston flow will run into hydrodynamic as well as mathematical difficulties. Abrupt changes in Ac will create secondary flows that invalidate the assumptions of piston flow. Thus reactors shaped like a megaphone are acceptable those with an abrupt change in diameter are not. 

Given 0 , find 0 for the megaphone reactor shown in Figure 3.1a. 

The radius of the megaphone varies linearly with z according to the equation... 

The fundamental concept of inductive and field effects introduced for carboxylic acids can be applied to weaker acids such as the a-hydrogen of ketones. Reaction of 12 with a strong base, in Zoretic s synthesis of megaphone,illustrates this premise. Both Ha and Hb in 12 are acidic, but Ha is preferentially removed by virtue of its proximity to the carbonyl (secs. 9.1, 9.2). Although Hb is acidic by the conjugating effect of the It bond (it is a vinylogous acid), the effect is diminished due to the distance from the carbonyl. Formation of the enolate is followed by alkylation (secs. 2.7.A, 9.3.A) to provide 13 in good yield. 

Fig. 7.3.10. Biogenesis of neolignans belonging to the bicyclo[3.2.1]octanoid (17, 23), futoenone (18,24), porosin (19), burchellin (25), and megaphone (20, 21) groups. Stereochemical indications are omitted in order to maintain the information as generally valid as possible...

Megaphon, Megafon (chemicals/alkali/acid) veratzei... 

Providing adequate communications equipment, e.g. a public address system or personal megaphones for fire marshals... 

Among parts recovered from the wreck of the Titanic, a megaphone in the form of a sawn-off cone was found, crimped at each end with a wire of—probably originally galvanised—steel. After 70 years in seawater at great depth, only part of the aluminium sheet in contact with the wire had been consumed. 

---