CID 4284

C₁₂H₁₇NO

DEET

C 12
H 17
N 1
O 1

Ball-and-stick Stick Space-filling

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31 atoms, 31 bonds.

IUPAC name: N,N-diethyl-3-methylbenzamide
Molar mass: 191.274(29) g/mol
Atoms: 31
SMILES: CCN(CC)C(=O)C1=CC=CC(=C1)C
InChIKey: MMOXZBCLCQITDF-UHFFFAOYSA-N
PubChem CID: 4284

Made of

C H N O

Structural formula of DEET. Each unlabelled corner is a carbon atom, and the eight hydrogens on carbon are not drawn. It shows which atoms are joined to which, not the shape. The model above shows the shape.

On paper, DEET forms when the carboxy group of m-toluic acid, its acidic COOH group, joins the nitrogen of diethylamine. That joining makes it an amide, filed among the benzamides by ChEBI (Chemical Entities of Biological Interest). The IUPAC name is N,N-diethyl-3-methylbenzamide, and the molar mass of 191.27 g/mol is shared among carbon, hydrogen, nitrogen and oxygen.

DEET itself is a clear, slightly viscous liquid, colourless to faintly yellow, with a faint and pleasant smell (CAMEO Chemicals, a US hazardous-materials database). At 0.996 g/cm³ and 20 °C, on the figure of the Hazardous Substances Data Bank (HSDB), it is just lighter than water, and a spill floats. Water does not dissolve it, yet it mixes in any proportion with ethanol, ether, chloroform and carbon disulfide. It also acts as a solvent on most plastics, paints and varnishes, and CAMEO lists rayon, acetate and dynel fabrics as incompatible with it.

Structure and bonding

The model’s 31 atoms form three regions. A six-carbon ring carries a methyl group, CH₃, at position 3, the meta position, two places along from where the ring meets the rest. There a carbon double-bonded to the lone oxygen leads to the nitrogen, which holds two ethyl groups. With Labels on, every H sits beside a C: the model has no N–H or O–H bond, the kind of bond hydrogen bonding depends on.

In Ball-and-stick, each ethyl and methyl carbon points four bonds at the corners of a tetrahedron, as Chem1 describes for carbon in most organic compounds. Each ring carbon, and the carbon bearing the oxygen, spreads three bonds in a flat triangle.

The ring is drawn with single and double bonds taking turns, one way of writing a benzene ring whose double-bond electrons are spread evenly round all six carbons. In the model, every ring bond measures 1.395 Å. Stick thins the frame to rods, and Space-filling merges the atoms into one outline, the ethyl groups bunched at the far end from the ring.

Where it turns up

Most commercial insect repellents carry DEET as their active ingredient, HSDB records, and ChEBI ranks it as the world’s most widely used insect repellent. The US Environmental Protection Agency (EPA) estimates that about a third of people in the United States use it. They guard against mosquito-borne West Nile virus, Zika and malaria, and tick-borne Lyme disease. It comes as lotions, sprays, roll-ons and towelettes. Cats, dogs, horses and the places pets live are treated with it too, but it has no use on food.

Showering or washing treated clothes can send it down the drain to sewage treatment and perhaps on into waterways, ATSDR (Agency for Toxic Substances and Disease Registry) says. In 1999 and 2000 the US Geological Survey sampled 139 streams in 30 states, chosen as likely to receive wastewater. DEET was among the chemicals found most often, in more than half of them. Levels were generally very low.

Why it matters

DEET began as a military chemical. The US Army developed it in 1946 for troops in insect-infested areas, and it was first registered in the United States in 1957, according to the EPA. In September 1988 the EPA called in more data, requiring further toxicity studies on animals and birds, and its reregistration decision followed in 1998. An interim decision came in September 2014, while the final one waits on an endocrine disruptor screening.

In the EPA’s account, DEET repels biting insects rather than killing them: it makes people hard for them to smell. Toxicity to insects is a separate action. In studies recorded by HSDB, DEET barely inhibited acetylcholinesterase, a nerve enzyme. It seemed instead to target synapses that signal with octopamine, junctions between nerve cells, and to overexcite insect nerves to toxic effect.

In rat brain cells, DEET also blocked the channels that let sodium and potassium ions through. HSDB suggests that this blocking may contribute to the numbness felt when DEET reaches the lips or mouth by accident.

Properties

Properties of DEET Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 4284.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₁₂H₁₇NO
Molar mass	191.274(29) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	12
Hydrogen atoms	17
Nitrogen atoms	1
Oxygen atoms	1
Bonds	31
Single bonds	27
Double bonds	4
PubChem molecular weight	191.27 g/mol	g/mol	PubChem

Safety

Harmful if swallowed and irritating to the skin and eyes, DEET carries the signal word Warning under the Globally Harmonized System (GHS), which rates the eye irritation as serious. HSDB describes it as strongly irritating to the eyes without being corrosive; MeSH (Medical Subject Headings) lists irritation of the eyes and mucous membranes but not of the skin. Based on extensive testing, the EPA judges normal use no health concern for the general population. The PubChem Laboratory Chemical Safety Summary for DEET collects its hazard classifications.

Questions

What is the chemical name of DEET?

Its IUPAC name, N,N-diethyl-3-methylbenzamide, reads like a map of the model. Benzamide is a six-carbon ring bonded to a carbon that holds a double-bonded oxygen and a nitrogen. N,N-diethyl puts two ethyl groups on that nitrogen, and 3-methyl places a CH₃ group at ring position 3, the meta position. Technical-grade DEET is almost entirely this meta isomer, according to the Hazardous Substances Data Bank.

Is DEET safe?

In 1998 the US Environmental Protection Agency (EPA) placed DEET in Toxicity Category III, second lowest of four: slightly toxic by eye, skin and mouth in animal tests. ATSDR, the Agency for Toxic Substances and Disease Registry, records reported reactions after excessive use of DEET repellents: skin irritation, seizures, poor coordination, agitation, aggression and low blood pressure. The EPA judged its own incident reports of the time too thin to establish DEET as the cause.

Does DEET cause cancer?

The EPA classifies DEET in Group D, meaning it is not classifiable as a human carcinogen, an agent that causes cancer. Long-term animal studies, with DEET given in food or put on the skin, found no rise in tumours, according to ATSDR. IARC, the International Agency for Research on Cancer, has given DEET no carcinogenicity classification.

Is DEET bad for the environment?

It does not linger in air: about half of the DEET there is gone within about 5 hours, broken down by reactions with other molecules, according to ATSDR. In water it does not evaporate; microorganisms break it down instead, and it does not build up in animals. The EPA rates it slightly toxic to fish, birds and water-dwelling invertebrates and practically non-toxic to mammals.

Made of the same elements

C₁₃H₁₆N₂O₂ Melatonin 33 atoms, 34 bonds.
C₁₃H₂₁NO₃ Albuterol 38 atoms, 38 bonds.
C₁₄H₁₈N₂O₅ Aspartame 39 atoms, 39 bonds.
C₁₄H₂₂N₂O Lidocaine 39 atoms, 39 bonds.
C₁₀H₁₂N₂O Serotonin 25 atoms, 26 bonds.
C₁₁H₁₂N₂O₂ Tryptophan 27 atoms, 28 bonds.
C₁₇H₂₁NO Diphenhydramine 40 atoms, 41 bonds.
C₉H₁₃NO₃ Epinephrine 26 atoms, 26 bonds.

All 25 compounds made of carbon, hydrogen, nitrogen and oxygen

C₉H₁₁NO₂ Phenylalanine 23 atoms, 23 bonds.
C₈H₁₁NO₂ Dopamine 22 atoms, 22 bonds.
C₆H₁₃NO₂ Isoleucine 22 atoms, 21 bonds.
C₆H₁₃NO₂ Leucine 22 atoms, 21 bonds.
C₉H₁₁NO₃ Tyrosine 24 atoms, 24 bonds.
C₈H₉NO₂ Acetaminophen 20 atoms, 20 bonds.
C₈H₁₀N₄O₂ Caffeine 24 atoms, 25 bonds.
C₂₀H₂₄N₂O₂ Quinine 48 atoms, 51 bonds.
C₅H₉NO₄ Glutamic acid 19 atoms, 18 bonds.
C₃H₇NO₂ Alanine 13 atoms, 12 bonds.
C₅H₆N₂O₂ Thymine 15 atoms, 15 bonds.
C₄H₅N₃O Cytosine 13 atoms, 13 bonds.
C₂H₅NO₂ Glycine 10 atoms, 9 bonds.
C₅H₅N₅O Guanine 16 atoms, 17 bonds.
C₄H₄N₂O₂ Uracil 12 atoms, 12 bonds.
CO(NH₂)₂ Urea 8 atoms, 7 bonds.
C₅H₄N₄O₃ Uric acid 16 atoms, 17 bonds.