5-Bromo-1-pentene
[CAS# 1119-51-3]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Hydrocarbon halide
• Name: 5-Bromo-1-pentene
• Molecular Formula: C₅H₉Br
• Molecular Weight: 149.03
• CAS Registry Number: 1119-51-3
• EC Number: 214-281-4
• SMILES: C=CCCCBr

Properties

• Density: 1.2±0.1 g/cm³, Calc.^*, 1.265 g/mL (Expl.)
• Index of Refraction: 1.46, Calc.^*, 1.463 (Expl.)
• Boiling Point: 126.2±9.0 °C (760 mmHg), Calc.^*, Melting point
• Flash Point: 31.0±6.7 °C, Calc.^*, 30 °C (Expl.)

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

Safety Data

• Hazard Symbols: GHS02;GHS07 Warning
• Risk Statements: H226-H315-H319-H335
• Safety Statements: P210-P233-P240-P241-P242-P243-P261-P264-P264+P265-P271-P280-P302+P352-P303+P361+P353-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P370+P378-P403+P233-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable liquids	Flam. Liq.	3	H226
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Eye irritation	Eye Irrit.	2A	H319
Acute toxicity	Acute Tox.	4	H302

• Transport Information: UN 1993

Discovery and Applications

5-Bromo-1-pentene is an organobromine compound with the molecular formula C₅H₉Br. It is a linear five-carbon alkene substituted with a bromine atom at the terminal carbon. The structure consists of a terminal alkene functional group (CH₂=CH−) and a bromine atom on the opposite terminal carbon (−CH₂Br), making it a useful bifunctional molecule in organic synthesis. The compound appears as a colorless to pale yellow liquid under standard laboratory conditions and is characterized by its reactivity due to the presence of both an alkene and a primary alkyl bromide.

5-Bromo-1-pentene can be synthesized by various methods, with one of the most direct routes involving the addition of hydrogen bromide to 1-pentyne under anti-Markovnikov conditions, followed by partial hydrogenation to yield the desired terminal alkene with a bromine substituent. Another common method includes the halogenation of 1-pentene or 5-pentanol derivatives, often utilizing phosphorus tribromide (PBr₃) or other brominating reagents to replace a hydroxyl group with a bromine atom.

The compound is frequently used as an intermediate in organic synthesis due to its dual functionality. The alkene moiety is amenable to a wide range of reactions, including hydroboration-oxidation, epoxidation, and olefin metathesis. Meanwhile, the bromine atom serves as a good leaving group in nucleophilic substitution reactions, allowing for the introduction of various functional groups such as amines, thiols, or alkoxides. This reactivity has made 5-bromo-1-pentene a valuable precursor in the synthesis of more complex molecules.

In the field of polymer chemistry, 5-bromo-1-pentene has been used to introduce functional side chains or cross-linkable units into polymer backbones. The presence of the alkene allows for copolymerization or further functionalization via radical or olefin-based processes. Its brominated end group can be exploited for grafting or chain extension reactions, particularly in controlled radical polymerization techniques like atom transfer radical polymerization (ATRP).

The compound is also employed in the preparation of heterocycles and other ring systems. The alkene can participate in cyclization reactions, while the bromine atom can undergo substitution to form nitrogen- or oxygen-containing rings. These transformations are commonly used in the development of pharmaceuticals and agrochemical intermediates, where the flexibility of the molecule supports a variety of synthetic strategies.

From a physical and safety perspective, 5-bromo-1-pentene is volatile and flammable, requiring careful handling in well-ventilated areas and the use of appropriate personal protective equipment. It is classified as an irritant to the eyes, skin, and respiratory tract. Standard laboratory precautions, including the use of gloves and eye protection, are recommended during its manipulation. The compound should be stored away from strong oxidizing agents and sources of ignition.

Toxicological studies indicate that exposure to 5-bromo-1-pentene may cause central nervous system depression and other symptoms typical of alkyl bromides. It is important to manage waste and emissions in accordance with local environmental regulations, as halogenated hydrocarbons can be persistent and toxic to aquatic life.

In conclusion, 5-bromo-1-pentene is a well-established reagent in organic and polymer chemistry. Its unique combination of alkene and alkyl bromide functionalities enables a wide variety of chemical transformations, making it a valuable building block in synthetic laboratories. Its applications are supported by consistent documentation in chemical literature and standard methodologies for its preparation and use.

References

2023. Chemical vapor deposition of carbohydrate-based polymers: a proof of concept study. Monatshefte für Chemie - Chemical Monthly, 154(2), 225-233.
DOI: 10.1007/s00706-022-03015-6

2022. NiH-catalyzed anti-Markovnikov hydroamidation of unactivated alkenes with 1,4,2-dioxazol-5-ones for the direct synthesis of N-alkyl amides. Communications Chemistry, 5(1), 167.
DOI: 10.1038/s42004-022-00791-4

2021. Replacing alkyl side chain of non-fullerene acceptor with siloxane-terminated side chain enables lower surface energy towards optimizing bulk-heterojunction morphology and high photovoltaic performance. Science China Chemistry, 64(8), 1350-1358.
DOI: 10.1007/s11426-021-9975-9