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Octane
Octane
is a hydrocarbon and an alkane with the chemical formula C8H18, and the condensed structural formula CH3(CH2)6CH3. Octane
Octane
has many structural isomers that differ by the amount and location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (isooctane) is used as one of the standard values in the octane rating scale. Octane
Octane
is a component of gasoline (petrol). As with all low-molecular-weight hydrocarbons, octane is volatile and very flammable.

Contents

1 Use of the term in gasoline 2 Metaphorical use 3 Isomers 4 References 5 External links

Use of the term in gasoline[edit] "Octane" is colloquially used as a short form of "octane rating" (an index of a fuel's ability to resist engine knock at high compression, which is a characteristic of octane's branched-chain isomers, especially iso-octane), particularly in the expression "high octane." The octane rating was originally determined by mixing a gasoline made entirely of heptane and 2,2,4-trimethylpentane (a highly branched octane), and assigning anti-knock ratings of 0 for pure heptane and 100 for pure 2,2,4-trimethylpentane. The anti-knock rating of this mixture would be the same as the percentage of 2,2,4-trimethylpentane in the mix. Modern octane ratings of gasoline are given octane ratings equal to those from this original heptane/octane scale. Different isomers of octane can contribute to a higher or lower octane rating. For example, n-octane (the straight chain of 8 carbon atoms with no branching) has a -10 (negative) octane rating, while pure 2,2,4-trimethylpentane (a highly branched octane) has an octane rating of 100.[4] Some fuels have an octane rating higher than 100, notably those containing methanol or ethanol. Metaphorical use[edit] Octane
Octane
became well known in American popular culture in the mid- and late 1960s, when gasoline companies boasted of "high octane" levels in their gasoline advertisements. The compound adjective "high-octane", meaning powerful or dynamic, is recorded in a figurative sense from 1944.[5] By the mid-1990s, the phrase was commonly being used as an intensifier and has found a place in modern English vernacular. Isomers[edit] Octane
Octane
has 18 structural isomers (24 including stereoisomers):

Octane
Octane
(n-octane) 2-Methylheptane 3-Methylheptane
3-Methylheptane
(2 enantiomers) 4-Methylheptane 3-Ethylhexane 2,2-Dimethylhexane 2,3-Dimethylhexane
2,3-Dimethylhexane
(2 enantiomers) 2,4-Dimethylhexane (2 enantiomers) 2,5-Dimethylhexane 3,3-Dimethylhexane 3,4-Dimethylhexane (2 enantiomers + 1 meso compound) 3-Ethyl-2-methylpentane 3-Ethyl-3-methylpentane 2,2,3-Trimethylpentane (2 enantiomers) 2,2,4-Trimethylpentane
2,2,4-Trimethylpentane
(isooctane) 2,3,3-Trimethylpentane 2,3,4-Trimethylpentane 2,2,3,3-Tetramethylbutane

References[edit]

^ "octane - Compound Summary". PubChem Compound. USA: National Center for Biotechnology Information. 16 September 2004. Identification and Related Records. Retrieved 6 January 2012.  ^ a b c d "NIOSH Pocket Guide to Chemical Hazards #0470". National Institute for Occupational Safety and Health (NIOSH).  ^ "Octane". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).  ^ eejit's guides – Octane
Octane
ratings explained ^ Oxford English Dictionary. 

External links[edit]

International Chemical Safety Card 0933 "NIOSH Pocket Guide to Chemical Hazards #0470". National Institute for Occupational Safety and Health (NIOSH).  Dr. Duke's Phytochemical and Ethnobotanical Databases, Octane, http://www.ars-grin.gov/cgi-bin/duke/chemical.pl?OCTANE

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Alkanes

Methane
Methane
(CH 4) Ethane (C 2H 6) Propane
Propane
(C 3H 8) Butane
Butane
(C 4H 10) Pentane
Pentane
(C 5H 12) Hexane
Hexane
(C 6H 14) Heptane
Heptane
(C 7H 16) Octane
Octane
(C 8H 18) Nonane
Nonane
(C 9H 20) Decane
Decane
(C 10H 22) Undecane
Undecane
(C 11H 24) Dodecane
Dodecane
(C 12H 26) Tridecane
Tridecane
(C 13H 28) Tetradecane
Tetradecane
(C 14H 30) Pentadecane
Pentadecane
(C 15H 32) Hexadecane
Hexadecane
/ Cetane (C 16H 34) Heptadecane
Heptadecane
(C 17H 36) Octadecane
Octadecane
(C 18H 38) Nonadecane
Nonadecane
(C 19H 40) Icosane
Icosane
(C 20H 42) Heneicosane
Heneicosane
(C 21H 44) Tetracosane
Tetracosane
(C 24H 50) Nonacosane
Nonacosane
(C 29H 60) Hentriacontane
Hentriacontane
(C 31H 64)

Higher alkanes List of alkanes

v t e

Binary compounds of hydrogen

Alkali metal hydrides

LiH NaH KH RbH CsH

Lithium hydride, LiH ionic metal hydride

Beryllium hydride Left (gas phase): BeH2 covalent metal hydride Right: (BeH2)n (solid phase) polymeric metal hydride

Borane
Borane
and diborane Left: BH3 (special conditions), covalent metalloid hydride Right: B2H6 (standard conditions), dimeric metalloid hydride

Methane, CH4 covalent nonmetal hydride

Ammonia, NH3 covalent nonmetal hydride

Water, H2O covalent nonmetal hydride

Hydrogen fluoride, HF covalent nonmetal hydride

Alkaline earth hydrides

Monohydrides

BeH MgH CaH SrH BaH

BeH2 MgH2 CaH2 SrH2 BaH2

Group 13 hydrides

Boranes

BH3 B2H6 B2H2 B2H4

Alanes

AlH3 Al2H6

Gallanes

GaH3 Ga2H6

Indiganes

InH3 In2H6

Thallanes

TlH3 Tl2H6

B2H2 B2H4 B4H10 B5H9 B5H11 B6H10 B6H12 B10H14 B18H22

Group 14 hydrides

Linear alkanes

CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18 C9H20 C10H22 more...

Linear alkenes

C2H4 C3H6 C4H8 C5H10 C6H12 C7H14 C8H16 C9H18 C10H20 more...

Linear alkynes

C2H2 C3H4 C4H6 C5H8 C6H10 C7H12 C8H14 C9H16 C10H18 more...

Silanes

SiH4 Si2H6 Si3H8 Si4H10 Si5H12 Si6H14 Si7H16 Si8H18 Si9H20 Si10H22 more...

Silenes

Si2H4

Silynes

Si2H2

Germanes

GeH4 Ge2H6 Ge3H8 Ge4H10 Ge5H12

Stannanes

SnH4 Sn2H6

Plumbanes

PbH4

CH CH2 CH3 C2H Cycloalkanes Cycloalkenes Annulenes Many more

Pnictogen hydrides

Azanes

NH3 N2H4 N3H5 N4H6 N5H7 N6H8 N7H9 N8H10 N9H11 N10H12 more...

Azenes

N2H2 N3H3 N4H4

Phosphanes

PH3 P2H4 P3H5 P4H6 P5H7 P6H8 P7H9 P8H10 P9H11 P10H12 more...

Phosphenes

P2H2 P3H3 P4H4

Arsanes

AsH3 As2H4

Stibanes

SbH3

Bismuthanes

BiH3

HN3 NH

radical

Hydrogen chalcogenides

Polyoxidanes

H2O H2O2 H2O3 H2O4 H2O5 H2O6 H2O7 H2O8 H2O9 H2O10 more...

Polysulfanes

H2S H2S2 H2S3 H2S4 H2S5 H2S6 H2S7 H2S8 H2S9 H2S10 more...

Selanes

H2Se H2Se2

Tellanes

H2Te H2Te2

Polanes

PoH2

HO HO2 HO3 H2O+–O– H2S=S (HS)2S+–S– HS HDO D2O T2O

Hydrogen halides

HF HCl HBr HI HAt

Transition metal hydrides

ScH2 YH2 YH3 TiH2 ZrH2 HfH2 VH VH2 NbH NbH2 TaH CrH CrH2 CrHx NiH PdHx (x < 1) FeH FeH2 FeH5 CuH ZnH2 CdH2 HgH2

Lanthanide hydrides

LaH2 LaH3 CeH2 CeH3 PrH2 PrH3 NdH2 NdH3 SmH2 SmH3 EuH2 GdH2 GdH3 TbH2 TbH3 DyH2 DyH3 HoH2 HoH3 ErH2 ErH3 TmH2 TmH3 YbH2 YbH2.5 LuH2 LuH3

Actinide hydrides

AcH2 ThH2 Th4H15 PaH3 UH3 NpH2 NpH3 PuH2 P

.