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<p>Rate coefficients for the reactions of OH radicals with C<span class="inline-formula">₃</span>–C<span class="inline-formula">₁₁</span> alkanes were determined using the multivariate relative-rate technique. A total of 25 relative-rate coefficients at room temperature and 24 Arrhenius expressions in the temperature range of 273–323 K were obtained. Notably, a new room temperature relative-rate coefficient for 3-methylheptane that had not been previously reported was determined, and the obtained <span class="inline-formula"><i>k</i>_OH</span> value (in units of <span class="inline-formula">10⁻¹²</span> cm<span class="inline-formula">³</span> molec.<span class="inline-formula">⁻¹</span> s<span class="inline-formula">⁻¹</span>) was 7.71 <span class="inline-formula">±</span> 0.35. Interestingly, whilst results for <i>n</i>-alkanes agreed well with available structure–activity relationship (SAR) calculations of Kwok and Atkinson (1995), Neeb (2000), Wilson et al. (2006), Jenkin et al. (2018), and McGillen et al. (2020), the three cycloalkanes (cyclopentane, methylcyclopentane, cyclohexane) and one branched alkane (2,2,4-trimethylpentane) were found to be less reactive than predicted by the SAR approach. Conversely, the SAR estimates for 2,3-dimethylbutane were approximately 25 % lower than the experimental values, with the exception of those estimated by the Wilson group, highlighting that there may be additional factors that govern the reactivity of highly branched alkanes that are not captured by current SAR techniques. Arrhenius expressions (in units of cm<span class="inline-formula">³</span> molec.<span class="inline-formula">⁻¹</span> s<span class="inline-formula">⁻¹</span>) for the reactions of various branched alkanes with OH radicals were determined for the first time: 2-methylheptane, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><mfenced close=")" open="("><mrow><mn mathvariant="normal">1.37</mn><mspace linebreak="nobreak" width="0.125em"/><mo>±</mo><mspace linebreak="nobreak" width="0.125em"/><mn mathvariant="normal">0.48</mn></mrow></mfenced><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">11</mn></mrow></msup><mi>exp⁡</mi><mfenced close="]" open="["><mrow><mo>-</mo><mfenced open="(" close=")"><mrow><mn mathvariant="normal">209</mn><mspace width="0.125em" linebreak="nobreak"/><mo>±</mo><mspace linebreak="nobreak" width="0.125em"/><mn mathvariant="normal">100</mn></mrow></mfenced><mo>/</mo><mi>T</mi></mrow></mfenced></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="214pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="230c78072a4ff592a3fe977bbdced2f5"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-11409-2024-ie00001.svg" width="214pt" height="17pt" src="acp-24-11409-2024-ie00001.png"/></svg:svg></span></span>, and 3-methylheptane, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow><mfenced close=")" open="("><mrow><mn mathvariant="normal">3.54</mn><mspace linebreak="nobreak" width="0.125em"/><mo>±</mo><mspace linebreak="nobreak" width="0.125em"/><mn mathvariant="normal">0.45</mn></mrow></mfenced><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">11</mn></mrow></msup><mi>exp⁡</mi><mfenced open="[" close="]"><mrow><mo>-</mo><mfenced open="(" close=")"><mrow><mn mathvariant="normal">374</mn><mspace linebreak="nobreak" width="0.125em"/><mo>±</mo><mspace linebreak="nobreak" width="0.125em"/><mn mathvariant="normal">49</mn></mrow></mfenced><mo>/</mo><mi>T</mi></mrow></mfenced></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="208pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="b849cae35cb3ce3d399dc44936ff7678"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-11409-2024-ie00002.svg" width="208pt" height="17pt" src="acp-24-11409-2024-ie00002.png"/></svg:svg></span></span>. The reactivity relation of saturated alkanes with OH radicals and chlorine atoms was obtained: <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M18" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>log⁡</mi><mn mathvariant="normal">10</mn></msub><mfenced close=")" open="("><mrow><msub><mi>k</mi><mrow class="chem"><mo>(</mo><mi mathvariant="normal">Cl</mi><mo>+</mo><mi mathvariant="normal">alkanes</mi><mo>)</mo></mrow></msub></mrow></mfenced><mo>=</mo><mn mathvariant="normal">0.569</mn><mo>×</mo><msub><mi>log⁡</mi><mn mathvariant="normal">10</mn></msub><mfenced close=")" open="("><mrow><msub><mi>k</mi><mrow class="chem"><mo>(</mo><mi mathvariant="normal">OH</mi><mo>+</mo><mi mathvariant="normal">alkanes</mi><mo>)</mo></mrow></msub></mrow></mfenced><mo>-</mo><mn mathvariant="normal">3.111</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="273pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="2f11effc84584d82477aad7d8b166e3a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-24-11409-2024-ie00003.svg" width="273pt" height="16pt" src="acp-24-11409-2024-ie00003.png"/></svg:svg></span></span> (<span class="inline-formula"><i>R</i>²</span> <span class="inline-formula">=</span> 0.86). In addition, the rate coefficients for the 24 previously studied OH <span class="inline-formula">+</span> alkanes reactions were consistent with existing literature values, demonstrating the reliability and efficiency of this method for the simultaneous investigation of gas-phase reaction kinetics.</p>