Standardizing Mechanisms: Friedel-Crafts Alkylation in SMILES

Continuing on the standardizing of mechanisms in SMILES. Friedel-Crafts is a common reaction to learn electrophilic substitution. The best explanation of the mechanism I found through this Reddit post from OchemWizz.

So let’s start writing this into SMILES

starting_product = 'O=C(C)C1=CC=CC=C1'
reactant_one = 'CC(Cl)C'
reactant_two = '[Al](Cl)(Cl)(Cl)'

The first step is the formation of the resonance structures.

first_resonance_structure = '[O-]/C(C)=C1C=CC=C[CH+]/1'
second_resonance_structure = '[O-]/C(C)=C1C=C[CH+]C=C/1'

This will help us determine states of a Friedels-Craft that are possible. Next ket’s prepare the 2-chloropropane. The lone pair on the chlorine coordinate to the aluminum and plucks off forming the carbocation propane.

aluminum_complex = 'CC(Cl~[Al](Cl)(Cl)Cl)C'
carbocation_propane = 'C[CH+]C'

Once this forms, the substitution can occur on the meta position which has the greatest nucleophilicity point.

first_step_mechanism = 'O=C(C)C1=CC(C(C)C)([H])[CH+]C=C1'

Then formation of the final product occurs with the clorine nucleophile attacking the hydrogen on the meta carbon and regenerating aromaticity which is more favorable as a driver, hydrochloric acid is also formed:

final_product = 'CC(C)C1=CC=CC(C(C)=O)=C1'

The full mechanism then can be recorded as an object where step is the resonance structures:

fridels_craft_acylation = {
    'reactants': ['CC(Cl)C', '[Al](Cl)(Cl)(Cl)']
    'step_1': 'O=C(C)C1=CC=CC=C1',
    'step_2': ['[O-]/C(C)=C1C=CC=C[CH+]/1', '[O-]/C(C)=C1C=C[CH+]C=C/1' ]
    'step_3': 'O=C(C)C1=CC(C(C)C)([H])[CH+]C=C1',
    'step_4': 'CC(C)C1=CC=CC(C(C)=O)=C1'
}