1-Bromopropane
[CAS# 106-94-5]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Hydrocarbon halide
• Name: 1-Bromopropane
• Synonyms: n-Propyl bromide; Propyl bromide
• Molecular Formula: C₃H₇Br
• Molecular Weight: 122.99
• CAS Registry Number: 106-94-5
• EC Number: 203-445-0
• SMILES: CCCBr

Properties

• Density: 1.3±0.1 g/cm³ Calc.^*, 1.354 g/mL (Expl.)
• Melting point: -110 °C (Expl.)
• Boiling point: 71.7±3.0 °C 760 mmHg (Calc.)^*, 71 °C (Expl.)
• Flash point: 25.6 °C (Calc.)^*, -6.1 °C (Expl.)
• Solubility: water 2.5 g/L (20 °C) (Expl.)
• Index of refraction: 1.432 (Calc.)^*, 1.432 - 1.438 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS02;GHS07;GHS08 Danger
• Risk Statements: H225-H315-H319-H335-H336-H360FD-H373
• Safety Statements: P203-P210-P233-P240-P241-P242-P243-P260-P261-P264-P264+P265-P271-P280-P302+P352-P303+P361+P353-P304+P340-P305+P351+P338-P318-P319-P321-P332+P317-P337+P317-P362+P364-P370+P378-P403+P233-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Flammable liquids	Flam. Liq.	2	H225
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Reproductive toxicity	Repr.	1B	H360
Specific target organ toxicity - single exposure	STOT SE	3	H335
Specific target organ toxicity - single exposure	STOT SE	3	H336
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Hazardous for the ozone layer	Ozone 99	1	H420
Specific target organ toxicity - single exposure	STOT SE	2	H371
Carcinogenicity	Carc.	2	H351
Reproductive toxicity	Repr.	1B	H360FD
Germ cell mutagenicity	Muta.	2	H341
Reproductive toxicity	Repr.	1B	H360FD

• Transport Information: UN 2344

Discovery and Applications

1-Bromopropane, commonly known as n-propyl bromide, is an organobromine compound that has attracted attention both as a useful chemical intermediate and as an industrial solvent. Its molecular formula is C₃H₇Br, and it belongs to the family of primary alkyl bromides, a group of compounds well known for their reactivity and role in organic synthesis. At room temperature, it is a colorless to pale yellow liquid with a density greater than that of water, a relatively low boiling point around 71–72 °C, and high volatility. These physical characteristics have contributed to its widespread industrial use in cleaning applications and chemical processes.

The chemistry of 1-bromopropane is governed by the highly polarized carbon–bromine bond. Bromine, being a large and electronegative atom, withdraws electron density from the carbon atom to which it is attached, rendering that carbon highly electrophilic. This makes the compound susceptible to nucleophilic attack, allowing it to undergo substitution reactions that form a wide variety of useful organic products. For example, in the presence of strong nucleophiles such as hydroxide, amines, or thiols, 1-bromopropane can yield propanol, propyl amines, or propyl thiols respectively. This capacity for substitution reactions makes it a versatile starting material in the synthesis of pharmaceuticals, agrochemicals, and specialty organic molecules. Under strongly basic conditions, the compound can also undergo elimination reactions to generate propene, a simple but industrially significant alkene.

The discovery and subsequent use of 1-bromopropane are closely tied to the development of halogenated hydrocarbons in the twentieth century. It became commercially significant when industries sought replacements for ozone-depleting substances such as chlorofluorocarbons and 1,1,1-trichloroethane. As international regulations restricted the use of those compounds, 1-bromopropane emerged as an alternative solvent for cleaning and degreasing operations, particularly in the electronics and metal industries. It was also incorporated into adhesives and aerosol products because of its effective solvency and favorable evaporation rate.

Despite these advantages, concerns about the safety and environmental impact of 1-bromopropane soon began to surface. Workers exposed to its vapors reported symptoms such as dizziness, headaches, reduced coordination, and cognitive difficulties, leading researchers to investigate its neurological effects. Laboratory studies confirmed that chronic exposure can damage the central nervous system, and later research linked the compound to reproductive toxicity and carcinogenicity. Animal experiments and occupational case studies indicated increased risks of infertility and cancer, prompting agencies to reassess its regulatory status. The U.S. National Toxicology Program classified it as reasonably anticipated to be a human carcinogen, and restrictions have been implemented to reduce occupational exposure.

The environmental behavior of 1-bromopropane further complicates its use. While it was initially marketed as a safer alternative to chlorofluorocarbons because it does not persist in the atmosphere for as long, it still contributes to air pollution and poses risks to ecosystems. Its volatility means that most emissions occur directly into the air, where it can degrade into reactive intermediates that affect atmospheric chemistry. Additionally, improper handling or disposal can contaminate soil and water, creating localized hazards for both humans and wildlife.

Nevertheless, 1-bromopropane continues to be studied and utilized as a model compound for understanding the chemistry and toxicology of halogenated hydrocarbons. In organic synthesis, its use as an alkylating agent remains important, especially in laboratory-scale reactions where controlled handling reduces exposure risks. Its straightforward reactivity has also made it a useful educational example in teaching fundamental principles of nucleophilic substitution and elimination.

The case of 1-bromopropane highlights the double-edged nature of chemical innovation. On one hand, it illustrates how a relatively simple modification to a small organic molecule—replacing a hydrogen atom with bromine—can yield a compound of significant industrial and synthetic utility. On the other hand, it demonstrates how the widespread adoption of new solvents and reagents requires careful evaluation of human health risks and environmental consequences. The compound’s trajectory from a promising replacement for regulated solvents to a substance under restriction underscores the need for sustainable chemical design, where performance, safety, and environmental responsibility are all taken into account.

Today, ongoing research into greener solvents and safer alternatives continues to reduce reliance on compounds like 1-bromopropane. Its history serves as a reminder that while chemical discoveries can provide immediate solutions to industrial challenges, their broader impacts must always be considered in the pursuit of long-term safety and sustainability.

References

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DOI: 10.1016/j.envres.2024.119586

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DOI: 10.1016/j.ecoenv.2024.116280

2024. Electrolyte Applications. Ionics, 30(4).
DOI: 10.1007/s11581-024-05889-4