4-Bromo(²H₄)benzonitrile: Properties, Uses & FAQs

4-bromo(²H₄)benzonitrile is a deuterium-labeled aromatic nitrile in which the four ring hydrogen atoms of 4-bromobenzonitrile are replaced by deuterium (²H), making it a valuable stable-isotope-labeled reagent for mechanistic studies, isotope tracing, quantitative NMR, and mass spectrometry-based analytics.

Chemical Name

4-Bromo(²H₄)benzonitrile (4-bromobenzonitrile-d4)

SKU / Catalog Number

B177413

Isotopic Labeling

Four aromatic hydrogen positions replaced by deuterium (²H); ring positions 2, 3, 5, 6

Key Functional Groups

Aryl bromide (C–Br) and nitrile (C≡N)

Primary Applications

Isotope tracing, quantitative MS, NMR standards, mechanistic organic chemistry

Isotope Effect Utility

Deuterium substitution provides a +4 Da mass shift relative to the unlabeled compound, enabling clear MS discrimination

What Is 4-Bromo(²H₄)benzonitrile?

4-Bromo(²H₄)benzonitrile, also referred to as 4-bromobenzonitrile-d4 (Aladdin SKU B177413), is the fully ring-deuterated isotopologue of 4-bromobenzonitrile. All four aromatic C–H bonds on the benzene ring are replaced by C–²H (C–D) bonds, while the aryl bromide and the cyano group remain chemically intact.

This compound belongs to the class of stable-isotope-labeled (SIL) reagents. Because deuterium is non-radioactive and chemically near-identical to protium, the compound handles and stores analogously to its unlabeled counterpart under standard laboratory conditions, yet it is spectroscopically and mass-spectrometrically distinguishable due to its shifted molecular mass (+4 Da) and characteristic C–D vibrational frequencies.

The simultaneous presence of two orthogonal reactive handles—the aryl bromide and the nitrile—makes this molecule particularly versatile in synthetic and mechanistic applications where isotopic tracking of the aromatic ring is required.

Spectroscopic and Physical Properties

Mass spectrometry: The molecular formula of the deuterated compound is C₇H₀D₄BrN, giving a nominal molecular weight approximately 4 Da higher than unlabeled 4-bromobenzonitrile (MW ≈ 182 g/mol for the protiated form). This clean mass shift is exploited in quantitative mass spectrometry workflows as an internal standard strategy.

NMR spectroscopy: Replacement of aromatic protons with deuterium eliminates the characteristic aromatic ¹H NMR signals of the ring, simplifying spectra in mechanistic reaction monitoring. ²H (deuterium) NMR can alternatively be used to confirm label integrity and isotopic purity.

IR spectroscopy: C–D stretching vibrations appear at lower wavenumbers (~2100–2300 cm⁻¹) compared to C–H stretches (~3000 cm⁻¹), providing a direct IR handle to confirm deuterium incorporation. The strong C≡N stretch near 2230 cm⁻¹ remains a characteristic absorption.

Physical state and handling: Like its unlabeled parent, 4-bromobenzonitrile-d4 is expected to be a white to off-white crystalline solid at room temperature. Storage recommendations typically follow those for halogenated aromatic nitriles: cool, dry conditions away from strong oxidizers and bases.

Applications in Research

Isotope tracing and metabolic studies: Deuterium-labeled aryl nitriles serve as isotopic tracers in pharmacokinetic and metabolic studies, allowing researchers to distinguish labeled substrate, metabolites, and products by mass spectrometry without the safety constraints associated with radioactive labels.

Internal standards for quantitative MS: Because 4-bromo(²H₄)benzonitrile is chemically near-identical to the unlabeled compound but distinguishable by mass, it is ideally suited as an internal standard in LC-MS/MS quantitation workflows, compensating for matrix effects and instrument variability.

Mechanistic organic chemistry: The compound enables kinetic isotope effect (KIE) studies when paired with protiated 4-bromobenzonitrile. KIE experiments can reveal whether C–H bond breaking is rate-determining in reactions involving the aromatic ring, such as electrophilic or nucleophilic aromatic substitutions.

Cross-coupling chemistry: The aryl bromide moiety makes this compound a direct deuterium-labeled substrate for palladium-catalyzed cross-coupling reactions (e.g., Suzuki, Negishi, Buchwald–Hartwig). Using the labeled compound allows tracking of the aryl fragment through multi-step synthetic sequences by MS or NMR.

Pharmaceutical and agrochemical research: Deuterium-labeled benzonitrile derivatives are used in drug metabolism studies and as synthetic building blocks for deuterium-enriched drug candidates, where isotopic substitution may modulate metabolic stability.

Ordering, Purity, and Storage Information

Catalog information: 4-Bromo(²H₄)benzonitrile is available from Aladdin Scientific under SKU B177413. Researchers are encouraged to verify current stock, available pack sizes, and pricing on the Aladdin Scientific website or by contacting customer service directly.

Isotopic purity: For SIL reagents, isotopic purity (atom % D) is a critical specification alongside chemical purity. Buyers should review the certificate of analysis (CoA) provided with each lot to confirm isotopic enrichment meets the requirements of their specific application. High isotopic purity (typically ≥98 atom % D) is generally required for quantitative MS internal standard applications.

Storage: Store in a cool, dry place, sealed under inert atmosphere if long-term stability is a concern. Avoid exposure to strong bases (which may hydrolyze the nitrile group) and moisture. Recommended storage temperature should be confirmed on the product CoA or label.

Regulatory and safety: As a halogenated organic compound, standard laboratory precautions apply. Consult the Safety Data Sheet (SDS) provided by Aladdin Scientific before use. The compound is intended for research use only and is not approved for human or veterinary therapeutic use.

Frequently Asked Questions Summary

The FAQ section below addresses the most common technical and procurement questions received about 4-bromo(²H₄)benzonitrile. Topics include the difference between isotopic and chemical purity, suitable analytical techniques for identity confirmation, compatibility with common coupling reactions, and guidance on selecting the right pack size for typical research workflows.

Frequently asked questions

What is the difference between chemical purity and isotopic purity for 4-bromo(²H₄)benzonitrile?

Chemical purity refers to the proportion of the sample that is the correct compound (4-bromobenzonitrile-d4) versus other chemical impurities, typically assessed by HPLC or GC. Isotopic purity (expressed as atom % D) describes the fraction of deuterium at each labeled position relative to all hydrogen isotopes present; a low isotopic purity means a significant portion of molecules carry protium at one or more ring positions, generating lower-mass isotopologues that can interfere with MS quantitation. For most quantitative MS applications, both high chemical purity and high isotopic purity (≥98 atom % D) are required—always consult the lot-specific Certificate of Analysis.

Can 4-bromo(²H₄)benzonitrile be used directly as an internal standard in LC-MS/MS quantitation?

Yes, 4-bromo(²H₄)benzonitrile is well suited as a stable-isotope-labeled internal standard for LC-MS/MS methods that target 4-bromobenzonitrile or structurally related analytes, because it co-elutes or elutes very close to the unlabeled analyte and compensates for matrix effects and extraction variability. The +4 Da mass shift provides sufficient separation of the labeled and unlabeled MRM transitions to avoid cross-talk. Researchers should validate the absence of back-exchange of deuterium under their specific sample preparation conditions.

Is 4-bromo(²H₄)benzonitrile compatible with palladium-catalyzed cross-coupling reactions?

Yes. The aryl C–Br bond is the reactive handle in palladium-catalyzed cross-couplings (e.g., Suzuki–Miyaura, Negishi, Buchwald–Hartwig amination), and deuterium on the aromatic ring does not significantly alter reactivity under standard cross-coupling conditions because C–D bonds at sp² aromatic carbons are not involved in the catalytic cycle. This makes the compound a useful deuterium-labeled building block for synthesizing isotopically labeled biaryl or arylamine products, which can subsequently be tracked by MS.

How should I confirm the identity and isotopic integrity of my 4-bromo(²H₄)benzonitrile lot upon receipt?

Upon receipt, verify the lot-specific Certificate of Analysis (CoA) for both chemical purity and atom % D values. Complementary in-house confirmation can be performed by high-resolution mass spectrometry (HRMS) to confirm the molecular ion cluster consistent with four deuterium substitutions, or by ¹H NMR to confirm the absence of aromatic proton signals in the ring region (7–8 ppm). IR spectroscopy can provide additional supporting evidence via the C–D stretching bands around 2100–2300 cm⁻¹.

What safety precautions should I follow when handling 4-bromo(²H₄)benzonitrile?

Handle 4-bromo(²H₄)benzonitrile using standard laboratory precautions for halogenated aromatic nitriles: wear appropriate PPE including gloves, lab coat, and safety glasses; work in a well-ventilated fume hood. Avoid inhalation of dust or vapors, skin contact, and ingestion. Consult the Safety Data Sheet (SDS) provided by Aladdin Scientific (SKU B177413) for specific hazard classifications, first-aid measures, and disposal requirements before beginning work.

References

1. General principles of stable isotope-labeled internal standards in LC-MS/MS quantitation — textbook-level knowledge; no specific citation assigned.
2. Kinetic isotope effects in aromatic substitution reactions — standard physical organic chemistry reference; specific source not cited.
3. Aladdin Scientific product page for 4-bromo(²H₄)benzonitrile, SKU B177413.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.