Octane (chemistry)

The octanes are a group of aliphatic, saturated hydrocarbons or alkanes that contain all eight carbon atoms in the molecule. The molecular formula of all octanes is C ₈ H ₁₈ .

Isomers

There are 18 isomeric octanes:

1. n- octane
2. 2-methylheptane
3. 3-methylheptane
4. 4-methylheptane
5. 2,2-dimethylhexane
6. 2,3-dimethylhexane
7. 2,4-dimethylhexane
8. 2,5-dimethylhexane
9. 3,3-dimethylhexane
10. 3,4-dimethylhexane
11. 3-ethylhexane
12. 2,2,3-trimethylpentane
13. 2,2,4-trimethylpentane ( iso- octane)
14. 2,3,3-trimethylpentane
15. 2,3,4-trimethylpentane
16. 3-ethyl-2-methylpentane
17. 3-ethyl-3-methylpentane
18. 2,2,3,3-tetramethylbutane

Structural formulas

In addition to the n- octane, three methylheptanes, six dimethylhexanes, one ethylhexane, four trimethylpentanes, two ethylmethylpentanes and one tetramethylbutane can be formulated.

Stereochemistry

3-methylheptane, 2,3-dimethylhexane, 2,4-dimethylhexane and 2,2,3-trimethylpentane have a stereocenter and are therefore chiral compounds. They each have two optically active (D / L) stereoisomers. 3,4-Dimethylhexane has two stereocenters. There are two optically active (D / L) stereoisomers and one meso form.

• 

  3-methylheptane

• 

  2,3-dimethylhexane

• 

  2,4-dimethylhexane

• 

  3,4-dimethylhexane

• 

  2,2,3-trimethylpentane

Physical Properties

Except for the 2,2,3,3-tetramethylbutane, the octane isomers are liquid at room temperature.

Comparison of physical properties of octanes (1)
Surname	n- octane	2-methylheptane	3-methylheptane	4-methylheptane	2,2-dimethylhexane	2,3-dimethylhexane	2,4-dimethylhexane	2,5-dimethylhexane	3,3-dimethylhexane
other names	Octane							Diisopropyl
Structural formula	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8th)	(9)
CAS number	111-65-9	592-27-8	589-81-1	589-53-7	590-73-8	584-94-1	589-43-5	592-13-2	563-16-6
			111002-96-1 [( R ) -enantiomer ]			393810-12-3 [( R ) -enantiomer ]	116836-51-2 [( R ) -enantiomer ]
			6131-25-5 [( S ) -enantiomer ]			393810-11-2 [( S ) -enantiomer ]	53990-98-0 [( S ) -enantiomer ]
PubChem	356			11512	11551	11447	11511	11592
Molecular formula	C 8 H 18
Molar mass	114.22 g mol −1
Brief description	colorless liquids
Melting point	−57 ° C	−110 ° C	−121 ° C (racemate)	−121 ° C	−121 ° C			−91 ° C	−126 ° C
boiling point	126 ° C	117 ° C	120 ° C	117 ° C	106 ° C	116 ° C	110 ° C	109 ° C	112 ° C
Vapor pressure (20 ° C)	14 hPa		40 hPa
Vapor pressure (30 ° C)	24.6 hPa						95 hPa
Vapor pressure (50 ° C)	67.2 hPa	95 hPa	95 hPa	95 hPa	145 hPa	103 hPa	135 hPa	135 hPa
Vapor pressure (65 ° C)			170 hPa	180 hPa	265 hPa	195 hPa	240 hPa	240 hPa
density	0.70 g cm −3	0.70 g cm −3	0.71 g cm −3	0.70 g cm −3	0.70 g cm −3	0.71 g cm −3	0.70 g cm −3	0.69 g cm −3	0.71 g cm −3
solubility	0.7 mg l −1 (20 ° C)	0.75 mg l −1 (20 ° C)	0.7 mg l −1 (20 ° C)	0.74 mg l −1 (25 ° C)	1.4 mg l −1 (25 ° C)	2.5 mg l −1 (20 ° C)	1.2 mg l −1 (25 ° C)	1.2 mg l −1 (25 ° C)	0.7 mg l −1 (20 ° C)
Flash point	12 ° C	6 ° C	6 ° C	6 ° C	−3 ° C	5 ° C	3 ° C	2 ° C
Lower explosion limit (LEL)	0.8% by volume	0.8% by volume	0.8% by volume	0.8% by volume	0.8% by volume		0.8% by volume	0.8% by volume
	38 g m −3	40 g m −3	40 g m −3	40 g m −3	40 g m −3		40 g m −3	40 g m −3
Upper explosion limit (UEL)	6.5% by volume	6.5% by volume	6.5% by volume	6.5% by volume	6.5% by volume		6.5% by volume	6.5% by volume
	310 g m −3	310 g m −3	310 g m −3	310 g m −3	310 g m −3		310 g m −3	310 g m −3
Ignition temperature	205 ° C		410 ° C			435 ° C

Comparison of physical properties of octanes (2)
Surname	3,4-dimethylhexane	3-ethylhexane	2,2,3-trimethylpentane	2,2,4-trimethylpentane	2,3,3-trimethylpentane	2,3,4-trimethylpentane	3-ethyl-2-methylpentane	3-ethyl-3-methylpentane	2,2,3,3-tetramethylbutane
other names				Isooctane					Hexamethylethane
Structural formula	(10)	(11)	(12)	(13)	(14)	(15)	(16)	(17)	(18)
CAS number	583-48-2	619-99-8	564-02-3	540-84-1	560-21-4	565-75-3	609-26-7	1067-08-9	594-82-1
	52919-17-2 [( R , R ) -enantiomer ]		54665-47-3 [( R ) -enantiomer ]
	10203-80-2 [( S , S ) -enantiomer ]		40824-48-4 [( S ) -enantiomer ]
	52949-33-4 [( 3R, 4S ) -enantiomer ]
PubChem	638048	12096		109070			11863	14018	11675
Molecular formula	C 8 H 18
Molar mass	114.22 g mol −1
Brief description	colorless liquids								firmly
Melting point			−112 ° C (racemate)	−107 ° C	−101 ° C	−110 ° C	−115 ° C	−91 ° C	100.8 ° C
boiling point	118 ° C	119 ° C	110 ° C	99 ° C	115 ° C	113 ° C	116 ° C	118 ° C	107 ° C (1020 hPa)
Vapor pressure (20 ° C)				53 hPa					29 hPa
Vapor pressure (30 ° C)									50.5 hPa
Vapor pressure (50 ° C)	100 hPa	95 hPa	140 hPa	200 hPa	120 hPa	120 hPa	110 hPa		134 hPa
Vapor pressure (65 ° C)	190 hPa	175 hPa	245 hPa	345 hPa	210 hPa	215 hPa	210 hPa
density	0.72 g cm −3	0.72 g cm −3	0.72 g cm −3	0.69 g cm −3	0.73 g cm −3	0.72 g cm −3	0.72 g cm −3	0.727 g cm −3	0.82 g cm −3
solubility	0.74 mg l −1 (20 ° C)	0.7 mg l −1 (20 ° C)	1.2 mg l −1 (25 ° C)	2.1 mg l −1 (20 ° C)	0.88 mg l −1 (25 ° C)	2.3 mg l −1 (25 ° C)	0.84 mg l −1 (20 ° C)	0.7 mg l −1 (20 ° C)	0.7 mg l −1 (20 ° C))
Flash point	5-10 ° C	5 ° C	3 ° C	−9 ° C	6 ° C	4 ° C	7 ° C		4 ° C
Lower explosion limit (LEL)	0.8% by volume			0.7% by volume		0.8% by volume			1.0% by volume
	40 g m −3			34 g m −3		40 g m −3
Upper explosion limit (UEL)	6.5% by volume			6.0% by volume		6.5% by volume
	310 g m −3			290 g m −3		310 g m −3
Ignition temperature			430 ° C	410 ° C	425 ° C		460 ° C

Individual evidence

1. ↑ ^{a b} all data were taken from the GESTIS database, the individual links are in the name line.
2. ^ Entry on octane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
3. ↑ Entry on 2-methylheptane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
4. ↑ Entry on 3-methylheptane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
5. ↑ Entry on 4-methylheptane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
6. ↑ Entry on 2,2-dimethylhexane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
7. ↑ Entry on 2,3-dimethylhexane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
8. ↑ Entry on 2,4-dimethylhexane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
9. ↑ Entry on 2,5-dimethylhexane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
10. ↑ Entry on 3,3-dimethylhexane in the GESTIS substance database of the IFA , accessed on October 20, 2010(JavaScript required) .
11. ↑ ^{a b} A. F. Forziati, AR Glasgow, CB Willingham, FD Rossini: Purification and properties of 29 paraffin, 4 alkylcyclopentane, 10-alkylcyclohexane, and 8 alkylbenzene hydrocarbons. In: Journal of Research of the National Bureau of Standards (United States). 36, 1946, pp. 129-136, doi: 10.6028 / jres.036.005 , (pdf)
12. ↑ D. Ciubotariu, M. Medeleanu, V. Vlaia, T. Olariu, C. Ciubotariu, D. Dragos, S. Corina: Molecular van der Waals Space and Topological Indices from the Distance Matrix. In: Molecules . 9, 2004, pp. 1053-1078, doi: 10.3390 / 91201053 .
13. ↑ Entry on 3,4-dimethylhexane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
14. ↑ Entry on 3-ethylhexane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
15. ↑ Entry on 2,2,3-trimethylpentane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
16. ↑ Entry on 2,2,4-trimethylpentane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
17. ↑ Entry on 2,3,3-trimethylpentane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
18. ↑ Entry on 2,3,4-trimethylpentane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
19. ↑ Entry on 3-ethyl-2-methylpentane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
20. ↑ Entry on 3-ethyl-3-methylpentane in the GESTIS substance database of the IFA , accessed on August 10, 2016(JavaScript required) .
21. ↑ Entry on 2,2,3,3-tetramethylbutane in the GESTIS substance database of the IFA , accessed on June 26, 2017(JavaScript required) .
22. ↑ DW Scott, DR Douslin, ME Gross, DG Oliver, HM Huffman: 2,2,3,3-tetramethyl Butane: Heat capacity, heats of transition, fusion and sublimation, vapor pressure, entropy and thermodynamic functions. In: J. Am. Chem. Soc. 74, 1952, pp. 883-887.