Fluorine substituted benzenes

Fluorine substituted benzenes
Benzene C 6 H 6
	6 ° C
	80 ° C
Fluorobenzene C 6 H 5 F
	−42 ° C
	85 ° C
Difluorobenzenes C 6 H 4 F 2
	o -	m -	p -
	−34 ° C	−59 ° C	−13 ° C
	92 ° C	82 ° C	88-89 ° C
Trifluorobenzenes C 6 H 3 F 3
	1,2,3-	1,2,4-	1,3,5-
	−4 ° C	−12 ° C	−5.5 ° C
	94-95 ° C	90 ° C	75-76 ° C
Tetrafluorobenzenes C 6 H 2 F 4
	1,2,3,4-	1,2,3,5-	1,2,4,5-
	−42 ° C	−46.25 ° C	4 ° C
	95 ° C	84.4 ° C	90 ° C
Pentafluorobenzene C 6 HF 5
	−47.4 ° C
	85.74 ° C
Hexafluorobenzene C 6 F 6
	3.7-4.1 ° C
	80-82 ° C

The fluorine-substituted benzenes are derived from benzene , in which one or more hydrogen atoms are replaced by a fluorine atom. This results in 12 different compounds that differ from one another in terms of degree of substitution and symmetry. These properties play the main role here and are shown in comparison.

A distinction is made according to the number of fluorine atoms and their position on the ring:

• (Mono-) fluorobenzene C ₆ H ₅ F
• Difluorobenzenes C ₆ H ₄ F ₂ , three structural isomers (1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene)
• Trifluorobenzenes C ₆ H ₃ F ₃ , three structural isomers (1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene)
• Tetrafluorobenzenes C ₆ H ₂ F ₄ , three structural isomers (1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene)
• Pentafluorobenzene C ₆ HF ₅
• Hexafluorobenzene C ₆ F ₆

properties

Boiling points

Overall, the boiling points change on average with each fluorine substituent added - in contrast to the methyl-substituted benzenes and the chlorine-substituted benzenes - only slightly (80 - 85 - ø 88 - ø 87 - ø 90 - 86 - 81). The boiling points of the three isomers of the di-, tri- and tetrafluorobenzenes are relatively close to one another and differ within a group by a maximum of 15 ° C. The symmetry is practically irrelevant here.

Melting points

With the melting points, the symmetry is particularly important. First of all, starting from benzene to fluorobenzene, the melting point drops significantly by around 50 ° C from +6 to −42 ° C - due to the introduction of a single fluorine substituent into the highly symmetrical benzene molecule.

In the di-, tri- and tetrafluorobenzenes p- difluorobenzene ( C 2 ), 1,3,5-trifluorobenzene ( C 3 ) and 1,2,4,5-tetrafluorobenzene ( C 2 ) are the representatives with the highest symmetry.

• Difluorobenzenes : The p- difluorobenzene, which has the highest symmetry, has the highest melting point of −13 ° C.
• Trifluorobenzenes : The melting points behave rather inconsistently compared to the difluorobenzenes. The most symmetrical representative in this group (1,3,5-trifluorobenzene) has a melting point of −5.5 ° C and thus differs little from the other two isomers. The comparatively low boiling point of 1,3,5-trifluorobenzene at 75-76 ° C is also noticeable.
• Tetrafluorobenzenes : Due to its symmetry, 1,2,4,5-tetrafluorobenzene has the highest melting point of 4 ° C.
• Pentafluorobenzene melts at −47.4 ° C. In comparison with the tetrafluorobenzenes , this is lower than that of 1,2,4,5-tetrafluorobenzene at 4 ° C due to the lower symmetry . The higher degree of substitution compared to the other two isomers is of no consequence here. There is only a slight difference to their melting points of −42 ° C and −46.25 ° C. More remarkable are the small differences between the melting and boiling points and its substitution inverse, fluorobenzene.
• With its melting point of 3.7–4.1 ° C and its boiling point of 80–82 ° C, hexafluorobenzene hardly differs from its substitution inverse, pure benzene.

density

The density increases continuously starting from the benzene (0.88 - 1.03 - ø 1.14 - ø 1.27 - ø 1.38 - 1.51 - 1.61).

Individual evidence

1. ↑ ^{a b c d} Entry on benzene in the GESTIS substance database of the IFA , accessed on December 28, 2019(JavaScript required) .
2. ↑ ^{a b c d} Entry on fluorobenzene in the GESTIS substance database of the IFA , accessed on December 28, 2019(JavaScript required) .
3. ↑ ^{a b} data sheet 1,2-difluorobenzene from Sigma-Aldrich , accessed on December 28, 2019 ( PDF ).
4. ↑ Entry on 1,3-difluorobenzene at ChemBlink , accessed on December 28, 2019.
5. ↑ ^{a b} data sheet 1,4-difluorobenzene from Sigma-Aldrich , accessed on December 28, 2019 ( PDF ).
6. ↑ Data sheet 1,3-difluorobenzene from Sigma-Aldrich , accessed on December 28, 2019 ( PDF ).
7. ↑ Entry on 1,2,3-trifluorobenzene at TCI Europe, accessed on December 28, 2019.
8. ↑ 1,2,4-trifluorobenzenes; CAS: 367-23-7 - 105624532 , German.alibaba.com, accessed December 28, 2019.
9. ↑ ^{a b} data sheet 1,3,5-trifluorobenzene from Sigma-Aldrich , accessed on December 28, 2019 ( PDF ).
10. ↑ Data sheet 1,2,3-trifluorobenzene from Sigma-Aldrich , accessed on December 28, 2019 ( PDF ).
11. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-500.
12. ↑ ^{a b} data sheet 1,2,3,4-tetrafluorobenzene from Sigma-Aldrich , accessed on December 28, 2019 ( PDF ).
13. ↑ ^{a b} David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-474.
14. ↑ ^{a b} data sheet 1,2,4,5-tetrafluorobenzene from Sigma-Aldrich , accessed on December 28, 2019 ( PDF ).
15. ↑ ^{a b c d} David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-414.
16. ↑ ^{a b c d} data sheet hexafluorobenzene from Sigma-Aldrich , accessed on December 28, 2019 ( PDF ).