W
Wacker process A process for the
manufacture of ethanal by the air oxidation of ethene. A mixture of air
and ethene is bubbled through a solution containing palladium(II) chloride and copper(II) chloride. The Pd
2+
ions form a complex with the ethene
in which the ion is bound to the pi
electrons in the C=C bond. This decreases the electron density in the
bond, making it susceptible to nucleophilic attack by water molecules.
The complex formed breaks down to
ethanal and palladium metal. The
Cu
2+ ions oxidize the palladium back
to Pd
2+ , being reduced to Cu
+ ions in
the process. The air present oxidizes
Cu
+ back to Cu
2+ . Thus the copper(II)
and palladium(II) ions effectively act
as catalysts in the process, which is
now the main source of ethanal and,
by further oxidation, ethanoic acid. It
can also be applied to other alkenes.
It is named after Alexander von
Wacker (1846–1922).
Wade’s rules A set of rules for predicting the structure of a cluster
compound based in the number of
electrons in the framework counted
in a particular way. The electrons
counted are known as skeletal electrons. The rules apply to polyhedra
that have triangular faces (known as
deltahedra). They were originally applied to the boron hydrides. Electron
pairs in bonding between two boron
atoms are counted as skeletal electrons but the pairs in B–H units are
ignored. However, if a boron atom is
connected to two hydrogens (BH 2 ),
the second bond is counted with the
skeletal electrons. According to the
rules, if the formula is [B n H n ]
2– and
there are n+1 skeletal electron pairs,
then the structure is closo. If the formula is
B n H n+4
and these are n+2 skeletal electron
pairs, the structure is nido. If the formula is
B n H n+6
and these are n+3 skeletal electron
pairs, the structure is arachno. The
rules are named after the British
chemist Kenneth Wade, who Ürst formulated them in the early 1970s.
Wagenaar test See acetone–
chlor–haemin test.
Wagner-Meerwein rearrangement A rearrangement in which an
alkyl group moves from a carbon
atom to an adjacent carbon atom
during a reaction. It often occurs to
stabilize a carbocation formed as an
intermediate during the reaction. Rearrangements of this type have been
extensively studied in terpene chemistry.
WAHUHA A pulse sequence in *nuclear magnetic resonance (NMR) used
to reduce linewidth. The WAHUHA
sequence (named after its inventors
Waugh, Huber, and Haberlen) effects
an averaging procedure by twisting
the magnetization vector in various
directions.
Walden’s rule An empirical rule
suggested by P. Walden (1863–1957)
concerning ions in solutions, stating
that the product of the molar conductivity, Λ m , and the viscosity, η, is
approximately constant for the same
ions in different solvents. Some
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Wacker process A process for the
manufacture of ethanal by the air oxidation of ethene. A mixture of air
and ethene is bubbled through a solution containing palladium(II) chloride and copper(II) chloride. The Pd
2+
ions form a complex with the ethene
in which the ion is bound to the pi
electrons in the C=C bond. This decreases the electron density in the
bond, making it susceptible to nucleophilic attack by water molecules.
The complex formed breaks down to
ethanal and palladium metal. The
Cu
2+ ions oxidize the palladium back
to Pd
2+ , being reduced to Cu
+ ions in
the process. The air present oxidizes
Cu
+ back to Cu
2+ . Thus the copper(II)
and palladium(II) ions effectively act
as catalysts in the process, which is
now the main source of ethanal and,
by further oxidation, ethanoic acid. It
can also be applied to other alkenes.
It is named after Alexander von
Wacker (1846–1922).
Wade’s rules A set of rules for predicting the structure of a cluster
compound based in the number of
electrons in the framework counted
in a particular way. The electrons
counted are known as skeletal electrons. The rules apply to polyhedra
that have triangular faces (known as
deltahedra). They were originally applied to the boron hydrides. Electron
pairs in bonding between two boron
atoms are counted as skeletal electrons but the pairs in B–H units are
ignored. However, if a boron atom is
connected to two hydrogens (BH 2 ),
the second bond is counted with the
skeletal electrons. According to the
rules, if the formula is [B n H n ]
2– and
there are n+1 skeletal electron pairs,
then the structure is closo. If the formula is
B n H n+4
and these are n+2 skeletal electron
pairs, the structure is nido. If the formula is
B n H n+6
and these are n+3 skeletal electron
pairs, the structure is arachno. The
rules are named after the British
chemist Kenneth Wade, who Ürst formulated them in the early 1970s.
Wagenaar test See acetone–
chlor–haemin test.
Wagner-Meerwein rearrangement A rearrangement in which an
alkyl group moves from a carbon
atom to an adjacent carbon atom
during a reaction. It often occurs to
stabilize a carbocation formed as an
intermediate during the reaction. Rearrangements of this type have been
extensively studied in terpene chemistry.
WAHUHA A pulse sequence in *nuclear magnetic resonance (NMR) used
to reduce linewidth. The WAHUHA
sequence (named after its inventors
Waugh, Huber, and Haberlen) effects
an averaging procedure by twisting
the magnetization vector in various
directions.
Walden’s rule An empirical rule
suggested by P. Walden (1863–1957)
concerning ions in solutions, stating
that the product of the molar conductivity, Λ m , and the viscosity, η, is
approximately constant for the same
ions in different solvents. Some
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