Ktl-icon-tai-lieu

Phẩm màu azo

Được đăng lên bởi thiennguyen3008
Số trang: 9 trang   |   Lượt xem: 893 lần   |   Lượt tải: 0 lần
1

Experiment 19: Combinatorial Synthesis of Azo Dyes
When a new pharmaceutical is needed to treat a medical condition, modern
chemists sometimes utilize a research technique known as combinatorial chemistry to
find molecules that have the necessary biological activity. In combinatorial chemistry, a
large number of structurally related compounds, called a library, is generated using a
single common reaction. The diversity of the compounds in the library can arise from
varying the substituents of the molecule, the functional groups or both. For instance, a
library of esters can be generated by reacting a variety of different alcohols and
carboxylic acids together. Once a library has been generated, the compounds must be
screened for the desired activity. An example of a class of drugs that was explored using
combinatorial methods are the benzodiazepines, which are used to treat anxiety disorders.
Two approaches to combinatorial syntheses are employed. In a parallel
synthesis, each compound is prepared individually, and the tests are performed
separately on each compound. In a split synthesis, the library of compounds is both
prepared and tested in mixtures of the compounds. In the latter case, the results of the
tests are complex and usually require deconvolution, although a savings is realized in
terms of time and materials. In either case, combinatorial chemistry allows the researcher
to draw conclusions about the relationship between structure and function in molecules.
The technique has been so successfully exploited that it is now utilized in other areas of
chemistry besides pharmaceutical research, including catalysis and materials research.
In this experiment, your lab section will generate a library of dye compounds
using a parallel synthesis. Each student will carry out the same reaction, but every
student in the laboratory will use a different pair of reactants. To screen the resulting
products, each student will make a dye bath from his or her compound and use it to dye a
variety of natural and man-made fabrics.
All of the dyes that will be synthesized contain an azo group:
N

N

The azo group joins together aromatic rings, resulting in an extended system of
conjugated multiple bonds, which is characteristic of all organic dyes.
Azo compounds are synthesized by first reacting a primary aromatic amine with
nitrous acid, HNO2, to produce an aryldiazonium ion:
Ar

N

N

This ion can couple with a nucleophilic aromatic compound, such as an aryl amine...
1
Experiment 19: Combinatorial Synthesis of Azo Dyes
When a new pharmaceutical is needed to treat a medical condition, modern
chemists sometimes utilize a research technique known as combinatorial chemistry to
find molecules that have the necessary biological activity. In combinatorial chemistry, a
large number of structurally related compounds, called a library, is generated using a
single common reaction. The diversity of the compounds in the library can arise from
varying the substituents of the molecule, the functional groups or both. For instance, a
library of esters can be generated by reacting a variety of different alcohols and
carboxylic acids together. Once a library has been generated, the compounds must be
screened for the desired activity. An example of a class of drugs that was explored using
combinatorial methods are the benzodiazepines, which are used to treat anxiety disorders.
Two approaches to combinatorial syntheses are employed. In a parallel
synthesis, each compound is prepared individually, and the tests are performed
separately on each compound. In a split synthesis, the library of compounds is both
prepared and tested in mixtures of the compounds. In the latter case, the results of the
tests are complex and usually require deconvolution, although a savings is realized in
terms of time and materials. In either case, combinatorial chemistry allows the researcher
to draw conclusions about the relationship between structure and function in molecules.
The technique has been so successfully exploited that it is now utilized in other areas of
chemistry besides pharmaceutical research, including catalysis and materials research.
In this experiment, your lab section will generate a library of dye compounds
using a parallel synthesis. Each student will carry out the same reaction, but every
student in the laboratory will use a different pair of reactants. To screen the resulting
products, each student will make a dye bath from his or her compound and use it to dye a
variety of natural and man-made fabrics.
All of the dyes that will be synthesized contain an azo group:
The azo group joins together aromatic rings, resulting in an extended system of
conjugated multiple bonds, which is characteristic of all organic dyes.
Azo compounds are synthesized by first reacting a primary aromatic amine with
nitrous acid, HNO
2
, to produce an aryldiazonium ion:
This ion can couple with a nucleophilic aromatic compound, such as an aryl amine or a
phenol, to produce the azo compound. On page 4, the top row of Table 1 shows the
primary amines that will be used for one reactant, and the first column in the table shows
the aryl phenol and secondary amine compounds that will be used for the other starting
material. The general sequence of reactions is shown at the top of page 2.
Dye molecules bind to the fiber molecules in cloth in one of the following ways:
via electrostatic attraction, by van der Waals forces, through hydrogen bonding or even
by covalent bonds. In general, the greater the number of polar groups that are present in
the fiber molecule, the easier the fabric is to dye. A variety of methods are available for
N N
Ar N N
Phẩm màu azo - Trang 2
Để xem tài liệu đầy đủ. Xin vui lòng
Phẩm màu azo - Người đăng: thiennguyen3008
5 Tài liệu rất hay! Được đăng lên bởi - 1 giờ trước Đúng là cái mình đang tìm. Rất hay và bổ ích. Cảm ơn bạn!
9 Vietnamese
Phẩm màu azo 9 10 917