Long-distance groups are included in the new GAV scheme to account for halogen/halogen and halogen/oxygen interactions on adjacent carbons. This modified group additivity approach was shown to significantly reduce errors in estimates of fluorinated and chlorinated hydrocarbons. To investigate their impact in this work, the long-distance interactions were removed from the ensemble of GAVs, and estimated ∆ f H • 298K without these groups were compared to estimates with the groups included for molecules in enum-halocarb4 that have halogens on adjacent carbons. Figure shows that, without the contributions from long-distance interactions, the GAVs systematically underestimate the ∆ f H • 298K of these molecules by over 5 kcal/mol on average. In other words, GAVs overpredict stability of HHCs if lacking a long-distance term to capture the destabilizing interaction between halogens or oxygens on adjacent carbons. This indicates that these long-distance interactions are essential to accurately predict thermochemical properties of HHCs using a group additive scheme.