Search results
Results from the WOW.Com Content Network
Cyclic acetals are very much more stable against acid hydrolysis than acyclic acetals. Consequently acyclic acetals are used practically only when a very mild cleavage is required or when two different protected carbonyl groups must be differentiated in their liberation.
These lines are important to the energy balance of planetary nebulae and H II regions. The forbidden 21-cm hydrogen line is particularly important for radio astronomy as it allows very cold neutral hydrogen gas to be seen. Also, the presence of [O I] and [S II] forbidden lines in the spectra of T-tauri stars implies low gas density.
Generic structure of acetals. In organic chemistry, an acetal is a functional group with the connectivity R 2 C(OR') 2. Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments not hydrogen. The two R' groups can be equivalent to each ...
Hückel's rule can also be applied to molecules containing other atoms such as nitrogen or oxygen. For example, pyridine (C 5 H 5 N) has a ring structure similar to benzene, except that one -CH- group is replaced by a nitrogen atom with no hydrogen. There are still six π electrons and the pyridine molecule is also aromatic and known for its ...
One method is to formally replace two hydrogen atoms by a methylene bridge (−CH 2 −); this gives the planar bicyclic 1,6-methano[10]annulene . Indeed, 1,6-methano[10]annulene has no bond length alternation in its X-ray structure and signs of a telltale diamagnetic ring current in its NMR spectrum . [ 3 ]
Pyramidal inversion in nitrogen and amines is known as nitrogen inversion. [8] It is a rapid oscillation of the nitrogen atom and substituents, the nitrogen "moving" through the plane formed by the substituents (although the substituents also move - in the other direction); [ 9 ] the molecule passing through a planar transition state . [ 10 ]
A second method of preparing organolithium reagents is a metalation (lithium hydrogen exchange). The relative acidity of hydrogen atoms controls the position of lithiation. This is the most common method for preparing alkynyllithium reagents, because the terminal hydrogen bound to the sp carbon is very acidic and easily deprotonated. [36]
Hexachlorophosphazene is a cyclic molecule, containing a P 3 N 3 core with alternating nitrogen and phosphorus atoms, and two additional chlorine atoms bonded to each phosphorus atom. Hexachlorophosphazene molecule contains six equivalent P–N bonds, for which the adjacent P–N distances are 157 pm .