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tokens: abundance used in our chemical reaction model. This table is from Garrod ( 2013 ). 4.2.2. The Physical Model The physical conditions used as input to the chemical model are based on the “fast warm-up model” from Garrod ( 2013 ). We have run four different models (A, B, C, and D) with different peak densities and/or temperatures as listed in Table 9 . The peak temperatures and densities were selected considering the recent observations toward hot cores (e.g., Hernández-Hernández et al. 2014 ). We will see how CH 2 NH formation processes depend on densities through the comparison of models A, B, and C, and on temperatures through the comparison of models A and D. The gas densities () were initially set to be 3 × 10 3 cm −3 , which gradually increased up to their peak densities along with the free-fall equation during the collapsing phase. While gas temperatures were fixed at 10 K in the collapsing phase, dust temperatures decreased from 16 to 8 K depending on the visual extinction, which was calculated from the gas density of the cloud. Once the peak densities were achieved, we fixed the densities, and the gas and dust temperatures were raised from ∼10 K to their peak temperatures in 7 × 10 4 years. Table 9 Peak Temperatures and Densities for the Models 4.2.3. Gas and Ice Phase Formation of CH<sub>2</sub>NH As a result of our model, CH 2 NH is formed both in the gas phase and on the dust grain surface. We summarize the main chemical reactions that form CH 2 NH on the surfaces in Table 10 . The dust surface reaction rates are proportional to both the probability of the reaction κ and the diffusion rates of reactant species (Hasegawa et al. 1992 ). κ is proportional to exp(- E ), where E A represents the value of the activation barrier. The diffusion rates depend on the exponential of the dust temperature. For the activation barriers of the hydrogenation processes of HCN and CH 2 NH, theoretically predicted values by Woon ( 2002 ) were employed. Table 10 Dust Surface Reactions Related to CH 2 NH Note. The dust surface reactions related to CH 2 NH are shown. E A represents the value of the activation barrier. Since radical species are so reactive, radical–radical reactions would have no activation barriers. The activation barriers for HCN and CH 2 NH were cited from the theoretical study by Woon ( 2002 ). The main reactions in the gas phase that form CH 2 NH are summarized in Table 11 . CH 2 NH is formed both by dissociative recombination processes and neutral–neutral reactions. The rate coefficients of gas-phase reactions are given by the Arrhenius equation, using the coefficients α , β , and γ :where T represents the gas temperature. As shown in Table 11 , the dissociative recombination processes have larger reaction rates. Table 11 Gas-phase Reactions Related to CH 2 NH Note. α , β , and γ represent the coefficients for the Arrhenius equation. 4.2.4. Modeling Results and Discussion The simulated gas-phase CH 2 NH abundances (relative to the