Chlorophyll a (C₅₅H₇₂MgN₄O₅) — Properties, Uses & Safety

Overview

Chlorophyll a (C55H72MgN4O5) is the primary photosynthetic pigment in plants, algae, and cyanobacteria, with a molar mass of 893.51 g/mol. It appears as a blue-black waxy solid in pure form but produces a brilliant green color in solution — the green color of leaves and grass is due to chlorophyll. The molecule has a complex structure centered on a porphyrin ring (a large, planar macrocyclic ring composed of four pyrrole subunits linked by methine bridges) with a magnesium ion (Mg2+) coordinated at its center. Attached to this ring is a long hydrophobic phytol tail that anchors the molecule in the thylakoid membranes of chloroplasts. Chlorophyll a absorbs light most strongly in the red (around 680 nm) and blue-violet (around 430 nm) regions of the visible spectrum, while reflecting and transmitting green light — which is why plants appear green. This selective light absorption drives the light-dependent reactions of photosynthesis, where chlorophyll captures photon energy and uses it to split water molecules and generate ATP and NADPH, ultimately powering the conversion of carbon dioxide into glucose (6 CO2 + 6 H2O → C6H12O6 + 6 O2). Chlorophyll has no significant GHS hazard classifications and is used as a natural green food coloring (E140) and in dietary supplements. For chemistry students, chlorophyll a is a masterclass in coordination chemistry (the Mg2+ center in the porphyrin ring), conjugated pi systems and their relationship to color and light absorption, spectroscopy (UV-Vis absorption spectra), photochemistry and energy transfer, and the biochemistry of photosynthesis. It connects inorganic chemistry (metal coordination), organic chemistry (heterocyclic aromatic compounds), and biology (energy conversion in living systems) in a single remarkable molecule that sustains nearly all life on Earth.

IUPAC Name

methyl (3S,4S)-3-[(1R)-1-(3,4-dihydroporphyrin-a-yl)ethyl]-4-formyl-3-(methoxycarbonyl)methyl-3,4-dihydroporphin-9-yl propionate

CAS Number

479-61-8

PubChem CID

14931

Molecular Formula

C₅₅H₇₂MgN₄O₅

Molar Mass

893.51 g/mol

State at STP

solid

Appearance

Blue-black waxy solid; bright green in solution