def get_rxns(db, id_list):
    """Returns reactions with associated IDs from a Mongo database.

    :param db: DB to search
    :type db: A Mongo Database
    :param id_list: IDs to get compounds for.
    :type id_list: list
    :return: Reaction JSON documents
    :rtype: list
    """
    reactions = []
    for rxn_id in id_list:
        reactions.append(db.reactions.find_one({'_id': rxn_id}))
    return reactions
