Bromothiophenes

Monobromothiophenes
Surname	2-bromothiophene	3-bromothiophene
other names	α-bromothiophene 2-thienyl bromide	β-bromothiophene 3-thienyl bromide
Structural formula
CAS number	1003-09-4	872-31-1
PubChem	13851	13383
Molecular formula	C 4 H 3 BrS
Molar mass	163.04 g mol −1
Physical state	liquid
description	colorless, clear, smelly liquid	light brown, clear, smelly liquid
Melting point	−10 ° C	<−10 ° C
boiling point	149-151 ° C	150 ° C
Flash point	52 ° C	52 ° C
density	1.684 g / cm 3 (25 ° C)	1.74 g / cm 3 (25 ° C)
Vapor pressure
solubility	not miscible with water
Refractive index	1.586 (20 ° C)	1.591 (20 ° C)
GHS labeling	danger	danger
H and P phrases	226-300-318	226-301-310-317 319-330-335
	no EUH phrases	no EUH phrases
	264-280-301 + 310 305 + 351 + 338	260-280-284-302 + 350 305 + 351 + 338-310
LD 50	35 mg kg −1 (oral, rat)	66–160 mg kg −1 (oral, rat)

Bromthiophenes is the collective term for two isomeric chemical compounds that belong to the heterocycles .

presentation

2-bromothiophene

The direct bromination of thiophene with elemental bromine yields not only 2-bromothiophene but also considerable amounts of 2,5-dibromothiophene . If the bromination is carried out with potassium bromate and hydrogen bromide , only simple substitution takes place .

3-bromothiophene

3-Bromothiophene can be prepared from 2,3,5-tribromothiophene , which is easily accessible by direct bromination of thiophene, by debromination with zinc dust in acetic acid .

Reactions

When 2-bromothiophene is treated with sodium amide in liquid ammonia , isomerization to 3-bromothiophene takes place.

The isomerization can with good yields with zeolite - catalysts are performed.

use

3-bromothiophene is the most important starting material for the synthesis of 3-substituted thiophenes.

Individual evidence

1. ↑ ^{a b c d e f g} data sheet 2-bromothiophene from Sigma-Aldrich , accessed on March 16, 2011 ( PDF ).
2. ↑ ^{a b c d e f g} Data sheet 3-bromothiophene from Sigma-Aldrich , accessed on March 16, 2011 ( PDF ).
3. ↑ ^{a b} Entry on 2-bromothiophene at ChemBlink , accessed on March 16, 2011.
4. ^ Entry on 3-bromothiophene in ChemicalBook , accessed on September 19, 2011.
5. ↑ Entry on 3-bromothiophene at ChemBlink , accessed on March 16, 2011.
6. ↑ YL Goldfarb, AA Dudinov, VP Litvinov: "New method for preparation of 2-bromothiophene," in Russian Chemical Bulletin , 1982 , 31  (10) pp 2104 to 2105; doi : 10.1007 / BF00950665 .
7. ^ ^{A b} A. R. Katritzky: Advances in Heterocyclic Chemistry , Verlag Academic Press, 1963 , ISBN 978-0-12020601-8 , p. 41 ( limited preview in the Google book search).
8. ↑ ^{a b} S. Gronowitz: “New Syntheses of 3-Bromothiophene and 3,4-Dibromothiophene”, in: Acta Chemica Scandinavica , 1959 , 13 , pp. 1045-1046; doi : 10.3891 / acta.chem.scand.13-1045 ; Full text (PDF file; 271 kB).
9. ↑ S. Gronowitz, T. Raznikiewicz: 3-Bromothiophene In: Organic Syntheses . 44, 1964, p. 9, doi : 10.15227 / orgsyn.044.0009 ; Coll. Vol. 5, 1973, p. 149 ( PDF ).
10. ↑ L. Brandsma, RLP de Jong: “A Large-Scale Procedure for the Preparation of 3-Bromothiophene from 2-Bromothiophene and Sodamide in Liquid Ammonia”, in: Synthetic Communications , 1990 , 20  (11), pp. 1697-1700 ; doi : 10.1080 / 00397919008053091 .
11. ↑ C. Werner, A. Kanschik-Conradsen, B. Kellermeier, H.-J. Schmidt: "Process for isomerization of 2-halothiophene to 3-halothiophene", United States Patent 7208610. Full text