Isoquinoline
Structural formula | ||||||||||||||||||||||
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Surname | Isoquinoline | |||||||||||||||||||||
other names |
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Molecular formula | C 9 H 7 N | |||||||||||||||||||||
Brief description |
colorless oily liquid or colorless flakes |
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properties | ||||||||||||||||||||||
Molar mass | 129.16 g mol −1 | |||||||||||||||||||||
Physical state |
firmly |
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density |
1.09 g cm −3 |
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Melting point |
26.5 ° C |
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boiling point |
243 ° C |
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Vapor pressure |
5 Pa (20 ° C) |
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solubility |
heavy in water (5 g l −1 at 20 ° C) |
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safety instructions | ||||||||||||||||||||||
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Toxicological data | ||||||||||||||||||||||
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Isoquinoline , also known as 2-azanaphthalene or benzo [ c ] pyridine , is an organic compound from the group of heteroaromatic compounds and belongs to the dinuclear heterocyclic parent systems. It consists of two fused aromatic six-membered rings - one benzene - and one pyridine ring - from which the empirical formula C 9 H 7 N results. Formally, it is therefore a naphthalene molecule in which a carbon atom of the ring structure has been replaced by a nitrogen atom . It is a structural isomer of quinoline .
The term isoquinoline encompasses a large class of chemical compounds that are derived from isoquinoline. Isoquinoline is the basic structure for a large number of naturally occurring alkaloids . Therefore, these alkaloids are also known as isoquinoline alkaloids . The isoquinoline base of these compounds is derived from the amino acid tyrosine .
Occurrence
Isoquinoline was first isolated from coal tar by Hoogewerf and van Dorp in 1885 . It could be separated by fractional crystallization of the sulfate. In 1914 Weissgerber developed a selective extraction process for the quick and elegant separation of isoquinoline. The process uses the property that isoquinoline is more basic than quinoline.
Extraction and presentation
Isoquinoline derivatives can be synthesized by a variety of different reactions. However, there are only a few direct syntheses for the synthesis of isoquinoline itself.
Pomeranz-Fritsch reaction
The Pomeranz-Fritsch reaction is an effective method for the synthesis of isoquinoline. It starts from benzaldehyde and aminoacetaldehyde diethylacetal and takes place in an acidic medium. Alternatively, benzylamine and glyoxal acetal can also be used.
Syntheses of isoquinoline derivatives
The following syntheses can be used for various isoquinoline derivatives:
- the Bischler-Napieralski reaction
- the Pictet-Gams reaction
- the Pictet-Spengler reaction (reaction of a phenylethylamine with an aldehyde with elimination of water to form tetrahydroisoquinoline and subsequent oxidation to isoquinoline)
properties
Isoquinoline is a colorless, hygroscopic liquid at room temperature , with a penetrating, unpleasant odor. Contaminated isoquinoline looks brownish. When it cools, it crystallizes out in platelets. The solubility in water is low, but it is very soluble in ethanol , acetone , diethyl ether and other typical organic solvents. As an organic base, it is readily soluble - with protonation - even in dilute acids.
As a chemical analogue of pyridine, isoquinoline is a weak base with a pK b value of 8.6. It is therefore easily protonated to form salts by strong acids such as hydrochloric acid. Isoquinoline forms adducts with Lewis acids such as boron trifluoride .
use
There are hardly any direct applications for isoquinoline itself. However, it is an important intermediate for a number of important isoquinoline derivatives. Examples are:
- Anesthetics such as dimethisoquine .
- Antihypertensives such as quinapril , Quinapirilat and debrisoquine. All derivatives of 1,2,3,4-tetrahydroisoquinoline.
- Fungicides such as 2,2'-hexadecamethylene diisoquinoline dichloride, which is also an antiseptic .
- Disinfectants such as N- laurylisoquinoline bromide
- Vasodilators such as papaverine
In addition, isoquinoline derivatives are widely used in the manufacture of dyes, insecticides , antimycotics and corrosion inhibitors .
Isoquinoline alkaloids
More than 600 isoquinoline alkaloids are known in nature, some of them with very high biological activity and pharmacological effectiveness. A selection of isoquinoline alkaloids:
- Papaverine
- Tubocurarine
- Berberine
- Laudanosine
- Reticulin
- Morphine
- Codeine
- Heroin (semi-synthetic)
- Dauricin
Ancistrocladus heyneanus (a tropical liana) contains a number of isoquinoline alkaloids, such as ancistrocladine .
literature
- TL Gilchrist: Heterocyclic Chemistry. 3. Edition. Addison-Wesley Longman, Essex, UK 1997.
- J. Harris, WJ Pope: iso quinoline and the iso quinoline-Reds. In: Journal of the Chemical Society . 121, 1922, pp. 1029-1033, doi: 10.1039 / CT9222101029 .
- AR Katritsky, AF Pozharskii: Handbook of Heterocyclic Chemistry. 2nd Edition. Elsevier, Oxford, UK 2000.
- AR Katritsky, CW Rees, EF Scriven (Eds.): Comprehensive Heterocyclic Chemistry II: A Review of the Literature 1982-1995. Vol. 5, Elsevier, Tarrytown, NY 1996.
- T. Nagatsu: Isoquinoline neurotoxins in the brain and Parkinson's disease. In: Neuroscience Research . 29, 1997, pp. 99-111. PMID 9359458 .
Web links
Individual evidence
- ↑ Entry on isoquinoline. In: Römpp Online . Georg Thieme Verlag, accessed on May 29, 2014.
- ↑ a b Isoquinoline data sheet (PDF) from Merck , accessed on October 1, 2010.
- ^ Brockhaus ABC chemistry. FA Brockhaus Verlag, Leipzig 1965, p. 594.
- ↑ a b c d e f Entry on isoquinoline in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
- ↑ a b c d quinoline alkaloids (alkaloids from tryptophan). ( Memento from May 29, 2014 in the Internet Archive ) a script from the University of Jena, WS 2006, natural product chemistry.
- ↑ Michael Dreyer: Isolation, characterization and stereochemical analysis of naphthylisoquinoline alkaloids and other natural products. Dissertation. 2004, DNB 973119896/34 .