2,2,4-Trimethylpentane

{{short description|Chemical compound}}

{{for|other isomers of octane|Octane#Isomers}}

{{Chembox

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 477209668

| ImageFile = 2,2,4-Trimethylpentane.svg

| ImageFile_Ref = {{chemboximage|correct|??}}

| ImageSize = 160

| ImageName = Skeletal formula of 2,2,4-trimethylpentane

| ImageFile1 = Isooctane-3D-balls.png

| ImageFile1_Ref = {{chemboximage|correct|??}}

| ImageSize1 = 160

| ImageName1 = Ball and stick model of 2,2,4-trimethylpentane

| ImageFile2 = Isooctane-3D-vdW.png

| ImageFile2_Ref = {{chemboximage|correct|??}}

| ImageSize2 = 160

| ImageName2 = Spacefill model of 2,2,4-trimethylpentane

| PIN = 2,2,4-Trimethylpentane{{cite web|title=2,2,4-trimethylpentane - Compound Summary|url=https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=10907&loc=ec_rcs#x291|work=PubChem Compound|publisher=National Center for Biotechnology Information|access-date=11 March 2012|location=USA|date=26 March 2005|at=Identification and Related Records}}

|Section1={{Chembox Identifiers

| CASNo = 540-84-1

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = QAB8F5669O

| PubChem = 10907

| ChemSpiderID = 10445

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| EINECS = 208-759-1

| UNNumber = 1262

| MeSHName = 2,2,4-trimethylpentane

| ChEBI = 62805

| ChEBI_Ref = {{ebicite|changed|EBI}}

| ChEMBL = 1797261

| ChEMBL_Ref = {{ebicite|changed|EBI}}

| RTECS = SA3320000

| Beilstein = 1696876

| SMILES = CC(C)CC(C)(C)C

| StdInChI = 1S/C8H18/c1-7(2)6-8(3,4)5/h7H,6H2,1-5H3

| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}

| StdInChIKey = NHTMVDHEPJAVLT-UHFFFAOYSA-N

| StdInChI_Ref = {{stdinchicite|correct|chemspider}}

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|Section2={{Chembox Properties

| C=8 | H=18

| Appearance = Colorless liquid

| Odor = petroleum-like

| Density = 0.692 g cm⁻³

| MeltingPtK = 165.77

| BoilingPtK = 372.45

| LogP = 4.373

| VaporPressure = 5.5 kPa (at 21 °C)

| HenryConstant = 3.0 nmol Pa⁻¹ kg⁻¹

| LambdaMax = 210 nm

| RefractIndex = 1.391

| MagSus = −98.34·10⁻⁶ cm³/mol

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|Section3={{Chembox Thermochemistry

| DeltaHf = −260.6 to −258.0 kJ mol⁻¹

| DeltaHc = −5462.6 to −5460.0 kJ mol⁻¹

| Entropy = 328.03 J K⁻¹ mol⁻¹

| HeatCapacity = 242.49 J K⁻¹ mol⁻¹

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|Section4={{Chembox Hazards

| GHSPictograms = {{GHS flame}} {{GHS exclamation mark}} {{GHS health hazard}} {{GHS environment}}

| GHSSignalWord = DANGER

| HPhrases = {{H-phrases|225|304|315|336|410}}

| PPhrases = {{P-phrases|210|261|273|301+310|331}}

| NFPA-H = 1

| NFPA-F = 3

| NFPA-R = 0

| FlashPtC = −12

| AutoignitionPtC = 396

| ExploLimits = 1.1–6.0%

}}

|Section5={{Chembox Related

| OtherFunction_label = alkanes

| OtherFunction = {{Unbulleted list|2,2-Dimethylbutane|2,3-Dimethylbutane|Triptane|Tetramethylbutane|Tetraethylmethane|2,3,3-Trimethylpentane|2,3,4-Trimethylpentane|Tetra-tert-butylmethane|2,3-Dimethylhexane|2,5-Dimethylhexane}}

}}

}}

2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an organic compound with the formula (CH₃)₃CCH₂CH(CH₃)₂. It is one of several isomers of octane (C₈H₁₈). This particular isomer is the standard 100 point on the octane rating scale (the zero point is n-heptane). It is an important component of gasoline, frequently used in relatively large proportions (around 10%) to increase the knock resistance of fuel.{{cite encyclopedia|author1=Werner Dabelstein |author2=Arno Reglitzky |author3=Andrea Schütze |author4=Klaus Reders|title=Automotive Fuels|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2007|publisher=Wiley-VCH|location=Weinheim|doi=10.1002/14356007.a16_719.pub2|isbn=978-3527306732 }}{{cite journal |last1=Richardson |first1=KA |last2=Wilmer |first2=JL |last3=Smith-Simpson |first3=D |last4=Skopek |first4=TR |title=Assessment of the genotoxic potential of unleaded gasoline and 2,2,4-trimethylpentane in human lymphoblasts in vitro. |journal=Toxicology and Applied Pharmacology |date=February 1986 |volume=82 |issue=2 |pages=316–22 |doi=10.1016/0041-008x(86)90207-3 |pmid=3945956}}

Strictly speaking, if the standard meaning of ‘iso’ is followed, the name isooctane should be reserved for the isomer 2-methylheptane. However, 2,2,4-trimethylpentane is by far the most important isomer of octane and historically it has been assigned this name.{{cite book|last=Clayden|first=Jonathan|title=Organic chemistry|year=2005|publisher=Oxford Univ. Press|location=Oxford [u.a.]|isbn=978-0-19-850346-0|pages=[https://archive.org/details/organicchemistry00clay_0/page/315 315]|edition=Reprinted (with corrections).|url-access=registration|url=https://archive.org/details/organicchemistry00clay_0/page/315}}