2-Fluorobenzyl chloride
[CAS 345-35-7]

Identification

• Classification: Organic raw materials >> Hydrocarbon compounds and their derivatives >> Hydrocarbon halide
• Name: 2-Fluorobenzyl chloride
• Synonyms: o-Fluorobenzyl chloride; alpha-Chloro-o-fluorotoluene; 1-(Chloromethyl)-2-fluoro-benzene
• Molecular Formula: C₇H₆ClF
• Molecular Weight: 144.58
• CAS Registry Number: 345-35-7
• EC Number: 206-460-0
• SMILES: C1=CC=C(C(=C1)CCl)F

Properties

• Density: 1.2±0.1 g/cm³ Calc.^*, 1.217 g/mL (Expl.)
• Boiling point: 176.4±15.0 °C 760 mmHg (Calc.)^*, 186.4 °C (Expl.)
• Flash point: 57.2 °C (Calc.)^*, 57 °C (Expl.)
• Index of refraction: 1.505 (Calc.)^*, 1.514 (Expl.)

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

Safety Data

• Hazard Symbols: GHS02;GHS05;GHS09 DangerGHS02
• Risk Statements: H226-H314-H318-H400-H410
• Safety Statements: P210-P233-P240-P241-P242-P243-P260-P264-P264+P265-P273-P280-P301+P330+P331-P302+P361+P354-P303+P361+P353-P304+P340-P305+P354+P338-P316-P317-P321-P363-P370+P378-P391-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable liquids	Flam. Liq.	3	H226
Skin corrosion	Skin Corr.	1A	H314
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Serious eye damage	Eye Dam.	1	H318
Skin corrosion	Skin Corr.	1B	H314
Eye irritation	Eye Irrit.	2	H319
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H302

chemBlink Chemical Story

2-Fluorobenzyl chloride, CAS 345-35-7, is a simple but useful bifunctional aromatic building block. NIST identifies it as 1-(chloromethyl)-2-fluorobenzene with formula C7H6ClF. The molecule contains two very different carbon-halogen bonds: a reactive benzylic C-Cl bond and a much less readily displaced aryl C-F bond.

That contrast is the key to its synthetic usefulness. The chloromethyl carbon is activated by the adjacent aromatic ring and can undergo nucleophilic substitution with oxygen-, nitrogen-, sulfur- and carbon-centered nucleophiles. In this way, an ortho-fluorobenzyl group can be attached to alcohols, amines, thiols or other synthetic partners. The aromatic fluorine usually remains intact during such substitution and becomes part of the final molecular architecture.

Fluorine is frequently introduced into medicinal and agrochemical molecules because replacing hydrogen with fluorine can alter lipophilicity, metabolic stability, conformation and electronic distribution without adding much steric bulk. 2-Fluorobenzyl chloride packages that fluorinated aromatic motif together with a convenient benzylic leaving group, making it a practical intermediate for exploring fluorinated analogues.

The ortho relationship also matters. Fluorine sits next to the benzylic substituent, so its electronic and steric influence differs from meta- or para-fluorobenzyl chloride. Positional isomers therefore cannot be treated as interchangeable even though they have the same elemental composition.

Public databases document the identity and physical/spectral properties of CAS 345-35-7, but they do not support assigning one dominant commercial end use. Its strongest description is therefore as a versatile fluorinated benzylating intermediate. The chlorine is designed to leave; the ortho-fluorobenzyl fragment is designed to remain.

References:
1. NIST Chemistry WebBook, Benzene, 1-(chloromethyl)-2-fluoro-, CAS 345-35-7.
2. PubChem, 2-Fluorobenzyl chloride, CAS 345-35-7.
3. Purser S et al. Fluorine in medicinal chemistry. Chem Soc Rev. 2008;37:320-330.

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