A reaction coordinate diagram plots potential energy against reaction progress, showing the energy landscape of a chemical transformation. The smooth curve traces the path from reactants through the transition state (energy maximum) to products, clearly depicting the activation energy barrier and overall enthalpy change. This fundamental chemistry visualization is essential for understanding reaction kinetics and thermodynamics.
""" anyplot.ai
line-reaction-coordinate: Reaction Coordinate Energy Diagram
Library: plotnine 0.15.7 | Python 3.13.14
Quality: 87/100 | Updated: 2026-06-24
"""
# ruff: noqa: E402
"""anyplot.ai — line-reaction-coordinate: Reaction Coordinate Energy Diagram
Library: plotnine | Python
"""
import os
import sys
_here = os.path.dirname(os.path.abspath(__file__))
sys.path = [p for p in sys.path if os.path.abspath(p or ".") != _here]
import numpy as np
import pandas as pd
from plotnine import (
aes,
annotate,
arrow,
element_blank,
element_line,
element_rect,
element_text,
geom_line,
geom_point,
geom_segment,
ggplot,
labs,
scale_x_continuous,
scale_y_continuous,
theme,
theme_minimal,
)
from scipy.interpolate import CubicSpline
# Theme-adaptive chrome tokens
THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"
# Imprint palette (hybrid-v3, 8 hues)
IMPRINT_PALETTE = ["#009E73", "#C475FD", "#4467A3", "#BD8233", "#AE3030", "#2ABCCD", "#954477", "#99B314"]
# Data — single-step exothermic reaction
reactant_energy = 50.0
transition_energy = 120.0
product_energy = 20.0
control_x = np.array([0.0, 0.10, 0.20, 0.35, 0.50, 0.65, 0.80, 0.90, 1.0])
control_y = np.array([50.0, 50.0, 55.0, 90.0, 120.0, 85.0, 30.0, 20.0, 20.0])
cs = CubicSpline(control_x, control_y)
reaction_coord = np.linspace(0, 1, 300)
energy = cs(reaction_coord)
curve_df = pd.DataFrame({"reaction_coord": reaction_coord, "energy": energy})
key_points = pd.DataFrame(
{"reaction_coord": [0.0, 0.50, 1.0], "energy": [reactant_energy, transition_energy, product_energy]}
)
# Arrow positions — balanced within data range
ea_x = 0.08 # Ea arrow, left side
dh_x = 0.82 # ΔH arrow, right side (room for label before edge)
# Annotation colors from Imprint palette (semantic roles)
ea_color = IMPRINT_PALETTE[4] # #AE3030 matte red — activation barrier (semantic: cost/warning)
dh_color = IMPRINT_PALETTE[2] # #4467A3 blue — enthalpy change
# Horizontal dashed reference lines at reactant and product energy levels
hline_df = pd.DataFrame(
{
"x": [0.0, 0.73],
"xend": [0.84, 0.84],
"y": [reactant_energy, product_energy],
"yend": [reactant_energy, product_energy],
}
)
arrow_head = arrow(length=0.12, type="closed")
plot = (
ggplot(curve_df, aes(x="reaction_coord", y="energy"))
# Dashed reference lines at reactant and product energy levels
+ geom_segment(
hline_df,
aes(x="x", y="y", xend="xend", yend="yend"),
linetype="dashed",
color=INK_MUTED,
size=0.4,
inherit_aes=False,
)
# Main energy curve — Imprint brand green (#009E73), first categorical series
+ geom_line(color=IMPRINT_PALETTE[0], size=1.5)
# Key-point markers at reactant, transition state, product
+ geom_point(
key_points,
aes(x="reaction_coord", y="energy"),
color=IMPRINT_PALETTE[0],
fill=IMPRINT_PALETTE[0],
size=3,
inherit_aes=False,
)
# Ea double-headed arrow (reactant level ↔ transition state)
+ annotate(
"segment",
x=ea_x,
xend=ea_x,
y=reactant_energy + 3,
yend=transition_energy - 3,
color=ea_color,
size=0.8,
arrow=arrow_head,
)
+ annotate(
"segment",
x=ea_x,
xend=ea_x,
y=transition_energy - 3,
yend=reactant_energy + 3,
color=ea_color,
size=0.8,
arrow=arrow_head,
)
+ annotate(
"text",
x=ea_x + 0.04,
y=(reactant_energy + transition_energy) / 2,
label="Eₐ = 70 kJ/mol",
size=3.5,
color=ea_color,
ha="left",
fontweight="bold",
)
# ΔH double-headed arrow (reactant level ↔ product level)
+ annotate(
"segment",
x=dh_x,
xend=dh_x,
y=reactant_energy - 2,
yend=product_energy + 2,
color=dh_color,
size=0.8,
arrow=arrow_head,
)
+ annotate(
"segment",
x=dh_x,
xend=dh_x,
y=product_energy + 2,
yend=reactant_energy - 2,
color=dh_color,
size=0.8,
arrow=arrow_head,
)
+ annotate(
"text",
x=dh_x + 0.03,
y=(reactant_energy + product_energy) / 2,
label="ΔH = −30\nkJ/mol",
size=3.5,
color=dh_color,
ha="left",
fontweight="bold",
)
# State labels
+ annotate(
"text",
x=0.02,
y=reactant_energy + 7,
label="Reactants\n50 kJ/mol",
size=3.5,
color=INK,
ha="left",
va="bottom",
fontweight="bold",
)
+ annotate(
"text",
x=0.50,
y=transition_energy + 6,
label="Transition State\n120 kJ/mol",
size=3.5,
color=INK,
ha="center",
va="bottom",
fontweight="bold",
)
+ annotate(
"text",
x=0.93,
y=product_energy - 5,
label="Products\n20 kJ/mol",
size=3.5,
color=INK,
ha="right",
va="top",
fontweight="bold",
)
+ labs(
title="line-reaction-coordinate · python · plotnine · anyplot.ai",
x="Reaction Coordinate",
y="Potential Energy (kJ/mol)",
)
+ scale_x_continuous(breaks=[0, 0.25, 0.5, 0.75, 1.0], labels=["0", "", "0.5", "", "1.0"], expand=(0.02, 0.08))
+ scale_y_continuous(limits=[0, 145], expand=(0.02, 0.02))
+ theme_minimal()
+ theme(
figure_size=(8, 4.5),
plot_title=element_text(size=12, ha="center", weight="bold", color=INK, margin={"b": 10}),
axis_title_x=element_text(size=10, color=INK_SOFT, margin={"t": 8}),
axis_title_y=element_text(size=10, color=INK_SOFT, margin={"r": 8}),
axis_text=element_text(size=8, color=INK_SOFT),
axis_line=element_line(color=INK_SOFT, size=0.4),
panel_grid_major_x=element_blank(),
panel_grid_minor=element_blank(),
panel_grid_major_y=element_line(color=INK, size=0.3, alpha=0.15),
plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
panel_background=element_rect(fill=PAGE_BG),
axis_ticks=element_blank(),
plot_margin=0.04,
)
)
plot.save(f"plot-{THEME}.png", dpi=400, width=8, height=4.5, units="in", verbose=False)
Part of Reaction Coordinate Energy Diagram on anyplot.ai.