Naptalam

Naptalam
Names
Preferred IUPAC name
N-1-naphthylphthalamic acid
Other names
  • Naptalam
  • Naptalam sodium
  • NPA
  • 2-[(1-naphthalenylamino)carbonyl]benzoic acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.153.563 Edit this at Wikidata
EC Number
  • 625-029-1
KEGG
UNII
  • InChI=1S/C18H13NO3/c20-17(14-9-3-4-10-15(14)18(21)22)19-16-11-5-7-12-6-1-2-8-13(12)16/h1-11H,(H,19,20)(H,21,22)
    Key: JXTHEWSKYLZVJC-UHFFFAOYSA-N
  • C1=CC=C2C(=C1)C=CC=C2NC(=O)C3=CC=CC=C3C(=O)O
Properties
C18H12NO3
Molar mass 290.298 g·mol−1
Appearance Purple solid[1]
Melting point 185 °C (acid), 234 °C (sodium salt)[1]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Severe eye irritant[2]
Lethal dose or concentration (LD, LC):
8200 mg/kg (acid), 1700 mg/kg (salt) (rat, oral)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Naptalam is a selective preëmergent herbicide, first registered in the US in 1949, to control sundry annual broadleaf weeds and grasses. Naptalam is a phthalic acid, though it is commonly also in sodium salt form.[1] It's also an aryl carboxylate, a phthalamate compound and an amide. It is also used in Australia[3] and Canada.[4] In 1974, the USA used 4.94 million pounds (2,240 t) in agriculture.[5]

Naptalam is unstable at temperatures over 180 °C or pH over 9.5.[1]

Naptalam's mode of action makes it a Group P or Group 19 herbicide under the HRAC classification.[3] It is absorbed through the weed's primary roots and seeds.[6]

Application

Naptalam has been used on soybean, peanut, cucumber and melon crops, and ornamentals. Typical application rates are 2 to 6 lbs per acre (active ingredient), (2.25-6.75 kg/Ha). Formulations are usually water based liquids, or granular.[1] While primarily preëmergent, naptalam may also be sprayed postemergently in some cases.[4] Preëmergently, it should be applied within 48 hours of planting; weeds already emerged will usually not be controlled. Light incorporation (to 0.5-1 inch deep) may help if the soil is dry. Postemergently, it is done before plants start to vine. It may stunt the crop growth, but it should return to normal. Emerged weeds may be stunted too, but are not usually controlled.[6]

It has been sold under the tradename "Alanap-L" and "Rescue" in the US, and has been manufactured by Uniroyal,[1] Chemtura and Vertac.[3][7] "Alanap-3" is a 240 g/L formulation sold in Canada.[4]

Environmental behaviour

In soil, naptalam is absorbed through the roots and translocated to the leaves. Soil mobility is high in fine sand, sandy loam, and silt loam; soil retention is increased with CEC and organic matter content.[1]

Naptalam's toxicity is low for birds, fish, and aquatic invertebrates, presenting minimal hazard.[1]

Safety

Naptalam is not carcinogenic, even at 5000 mg/kg, the highest dose tested on mice. It has some teratogenicity, so the EPA recommends a NOEL of 15 mg/kg/day. However, it causes irreversible eye damage, and is corrosive.[1]

References

  1. ^ a b c d e f g h i j "Pesticide Fact Sheet: Naptalam, 1985". nepis.epa.gov. US EPA.
  2. ^ "Pesticide Poisoning Action Guide Agricultural Pesticide In The Midwest Resource Directory 1994". nepis.epa.gov. US EPA.
  3. ^ a b c Hertfordshire, University of. "Naptalam (Ref: ACP 322)". sitem.herts.ac.uk.
  4. ^ a b c "ALANAP-3 LABEL" (PDF). bartlett.ca. Retrieved 4 May 2025.
  5. ^ "Pesticide Usage Survey, of Agricultural, Governmental and Industrial Sectors in the United States, 1974". nepis.epa.gov. Retrieved 3 May 2025.
  6. ^ a b "Pesticide Product Label, ALANAP-L, 07/07/2003" (PDF). US EPA. Retrieved 3 July 2025.
  7. ^ "Pesticide Reregistration Progress Report 1992". nepis.epa.gov. NSCEP. Retrieved 3 May 2025.
  • Naptalam in the Pesticide Properties DataBase (PPDB) (Naptalam)
  • Naptalam in the Pesticide Properties DataBase (PPDB) (Naptalam-sodium)

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