cessfully be used for mixed ethers
only when one alcohol is primary
and the other tertiary (otherwise a
mixture of the three possible products results). 2. A method of preparing ethers by reacting a haloalkane
with an alkoxide. The reaction, discovered in 1850, is a nucleophilic
substitution in which the negative
alkoxide ion displaces a halide ion;
for example:
RI +
– OR′ → ROR′ + I
–
A mixture of the reagents is reÛuxed
in ethanol. The method is particularly useful for preparing mixed
ethers, although a possible side reaction under some conditions is an
elimination to give an alcohol and an
alkene.
Wiswesser line notation (WLN)
An early *line notation for chemical
structures. The symbols used are the
upper-case letters of the alphabet
(A–Z), the numerals (0–9), with three
other symbols: the ampersand (&),
the hyphen (-), and the oblique stroke
(/), and a blank space. Atomic symbols with one letter, such as B and F,
are unchanged. Frequently occurring
elements with more than one letter
and functional groups are also assigned one letter; for example, G
stands for chlorine, Q for hydroxyl,
and Z for NH 2 . The numerals indicate
the number of carbon atoms in an
unbranched internally saturated
alkyl chain. For example, CH 3 is denoted 1 and CH 3 CH 2 is denoted 2. To
establish the notation of a compound
the characters for the fragments are
given in an established order. For example, the notation for C 2 H 5 OH is
Q2. Rules for structures with
branched chains and fused rings are
also given. WLN provides a short and
unambiguous notation, which is suitable for database searches.
witherite A mineral form of *barium carbonate, BaCO 3 .
WLN See wiswesser line notation.
Wöhler, Friedrich (1800–82) German physician and chemist, who became a professor of chemistry at
Göttingen. In 1828 he made his bestknown discovery, the synthesis of
urea (an organic compound) from
ammonium cyanate (an inorganic
salt). This Ünally disproved the assertion that organic substances can be
formed only in living things. Wöhler
also isolated aluminium (1827), beryllium (1828), and yttrium (1828).
Wöhler’s synthesis A synthesis of
urea performed by Friedrich Wöhler
in 1828. He discovered that urea
(CO(NH 2 ) 2 ) was formed when a solution of ammonium isocyanate
(NH 4 NCO) was evaporated. At the
time it was believed that organic substances such as urea could be made
only by living organisms, and its production from an inorganic compound was a notable discovery. It is
sometimes (erroneously) cited as ending the belief in vitalism.
wolfram See tungsten.
wolframite (iron manganese tungsten) A mineral consisting of a
mixed iron–manganese tungstate,
(FeMn)WO 4 , crystallizing in the
monoclinic system; the principal ore
of tungsten. It commonly occurs as
blackish or brownish tabular crystal
groups. It is found chieÛy in quartz
veins associated with granitic rocks.
China is the major producer of wolframite.
wood alcohol See methanol.
Wood’s metal A low-melting
(71°C) alloy of bismuth (50%), lead
(25%), tin (12.5%), and cadmium
(12.5%). It is used for fusible links in
automatic sprinkler systems. The
melting point can be changed by
557
Wood’s metal
w
www.AzShimi.ir www.AzShimi.com
only when one alcohol is primary
and the other tertiary (otherwise a
mixture of the three possible products results). 2. A method of preparing ethers by reacting a haloalkane
with an alkoxide. The reaction, discovered in 1850, is a nucleophilic
substitution in which the negative
alkoxide ion displaces a halide ion;
for example:
RI +
– OR′ → ROR′ + I
–
A mixture of the reagents is reÛuxed
in ethanol. The method is particularly useful for preparing mixed
ethers, although a possible side reaction under some conditions is an
elimination to give an alcohol and an
alkene.
Wiswesser line notation (WLN)
An early *line notation for chemical
structures. The symbols used are the
upper-case letters of the alphabet
(A–Z), the numerals (0–9), with three
other symbols: the ampersand (&),
the hyphen (-), and the oblique stroke
(/), and a blank space. Atomic symbols with one letter, such as B and F,
are unchanged. Frequently occurring
elements with more than one letter
and functional groups are also assigned one letter; for example, G
stands for chlorine, Q for hydroxyl,
and Z for NH 2 . The numerals indicate
the number of carbon atoms in an
unbranched internally saturated
alkyl chain. For example, CH 3 is denoted 1 and CH 3 CH 2 is denoted 2. To
establish the notation of a compound
the characters for the fragments are
given in an established order. For example, the notation for C 2 H 5 OH is
Q2. Rules for structures with
branched chains and fused rings are
also given. WLN provides a short and
unambiguous notation, which is suitable for database searches.
witherite A mineral form of *barium carbonate, BaCO 3 .
WLN See wiswesser line notation.
Wöhler, Friedrich (1800–82) German physician and chemist, who became a professor of chemistry at
Göttingen. In 1828 he made his bestknown discovery, the synthesis of
urea (an organic compound) from
ammonium cyanate (an inorganic
salt). This Ünally disproved the assertion that organic substances can be
formed only in living things. Wöhler
also isolated aluminium (1827), beryllium (1828), and yttrium (1828).
Wöhler’s synthesis A synthesis of
urea performed by Friedrich Wöhler
in 1828. He discovered that urea
(CO(NH 2 ) 2 ) was formed when a solution of ammonium isocyanate
(NH 4 NCO) was evaporated. At the
time it was believed that organic substances such as urea could be made
only by living organisms, and its production from an inorganic compound was a notable discovery. It is
sometimes (erroneously) cited as ending the belief in vitalism.
wolfram See tungsten.
wolframite (iron manganese tungsten) A mineral consisting of a
mixed iron–manganese tungstate,
(FeMn)WO 4 , crystallizing in the
monoclinic system; the principal ore
of tungsten. It commonly occurs as
blackish or brownish tabular crystal
groups. It is found chieÛy in quartz
veins associated with granitic rocks.
China is the major producer of wolframite.
wood alcohol See methanol.
Wood’s metal A low-melting
(71°C) alloy of bismuth (50%), lead
(25%), tin (12.5%), and cadmium
(12.5%). It is used for fusible links in
automatic sprinkler systems. The
melting point can be changed by
557
Wood’s metal
w
www.AzShimi.ir www.AzShimi.com