astronomy

Galaxolide

Galaxolide is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Galaxolide rather than just read about it. In short: Galaxolide (trade name; also known as Abbalide, Pearlide, Astrolide, Musk 50, Polarlide; chemical name 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8,-hexamethyl-cyclopenta[g]benzopyran or HHCB, hexamethylindanopyran) is a synthetic musk with a clean sweet musky floral woody odor used in fragrances. It is one of the musk components that perfume and cologne manufacturers use to add a musk odor to their products.

Key takeaways

Galaxolide belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Galaxolide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Galaxolide from memory before moving on to harder problems.

Reference excerpt

Galaxolide (trade name; also known as Abbalide, Pearlide, Astrolide, Musk 50, Polarlide; chemical name 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8,-hexamethyl-cyclopenta[g]benzopyran or HHCB, hexamethylindanopyran) is a synthetic musk with a clean sweet musky floral woody odor used in fragrances. It is one of the musk components that perfume and cologne manufacturers use to add a musk odor to their products. Galaxolide was first synthesized in 1956, and used in the late 1960s in some fabric softeners and detergents. High concentrations were also incorporated in fine fragrances.

Chemistry Galaxolide is the trade name from International Flavors & Fragrances Inc. (IFF) for the fragrance material with CAS Registry Number 1222-05-5 and CAS chemical name 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta[g]-2-benzopyran. Galaxolide is also known by its IUPAC name 4,6,6,7,8,8-hexamethyl-1,3,4,6,7,8-hexahydro-cyclopenta[g]-isochromene and the more commonly used acronym of the chemical name 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8,-hexamethyl-cyclopenta[g]benzopyran (HHCB). The abbreviation for this chemical name, HHCB, is commonly used for galaxolide in various publications. Galaxolide may also be known as hexamethylindanopyran under the International Nomenclature of Cosmetic Ingredients (INCI).

Physical-chemical properties Galaxolide is a mixture of isomers. It has chiral centers at carbon atom 4 and 7. The isomers are (4R,7R), (4R,7S), (4S,7S) and (4S, 7R). Galaxolide has a molecular formula of C18H26O and a molecular weight of 258.4 g/mol. At room temperature, it occurs as a highly viscous liquid. Its melting point is -20 °C and its boiling point is estimated to be 330 °C based on a boiling point of 160 °C at 4 hPa.

History Galaxolide was discovered at IFF in the 1960s, by Heeringa and Beets. It was first synthesized in 1965 and its discovery was mainly due to the work by Beets on the osmophoric group of the polycyclic musks, where they tried to improve existing synthetic musks by making them more stable and hydrophobic.

Odor Galaxolide has become the key synthetic musk ingredient belonging to the polycyclic musk group as defined by the International Fragrance Association (IFRA). Its odor is described as a “clean”, sweet, floral, woody musk. Galaxolide is a mixture of stereoisomers and research has shown that it is in particular the (4S,7R) and (4S, 7S) forms that are the most powerful musk notes, with odor thresholds of 1 ng/L or less.

Environmental data Galaxolide has a measured bioconcentration factor (BCF) in fish in a range of 600-1600 and a log octanol-water partition coefficient (Log Kow) of around 5.5 (5.3 – 5.9). Given its lack of bioaccumulation and toxicity, the EU determined that galaxolide does not meet the criteria for being a substance classified as Persistent, Bioaccumulative and Toxic (PBT) to the environment. However, the EPA's assessment of galaxolide found it to be moderately persistent and bioaccumulative and highly toxic to aquatic organisms. The EPA's PBT Profiler also finds Galaxolide to exceed the EPA's criteria as a PBT. Galaxolide degrades in the environment to primary degradants with log Kow < 4 and further to more hydrophilic products with log Kow of < 1. Galaxolide is classified as H410: "Very toxic to aquatic life with long lasting effects." under EU CLP classification rules. Although there have been reports of galaxolide in environmental compartments, these studies have been made part of galaxolide's environmental safety reviews by various authorities, who have deemed that there is no need for risk reduction measures. Galaxolide contamination has been detected in the Great Lakes. In a study of lake sediment in Lake Erie found galaxolide levels to be doubling every 8–16 years, raising question of its bioaccumulative properties. Galaxolide was detected in 92% of water samples from Lake Michigan. In 2015 a GreenScreen for Safer Chemicals assessment of Galaxolide assigned Galaxolide a score of Benchmark 1. Benchmark 1 is assigned to chemicals of highest concern whose use is recommended to be avoided. Specifically, the GreenScreen assigned the Benchmark 1 score due to Galaxolide's high persistent, bioaccumulative and aquatic toxicity properties. Galaxolide has been shown to be removed by ozonation in wastewaters treatment plants. Yet, studies show, it is commonly detected in rivers, drinking water, lake sediment and fish tissue.

Human health Galaxolide is not an irritant, not toxic, not a CMR substance nor a sensitizer. Based on test data, the EU Scientific Committee for Consumer Safety included galaxolide in their proposal for extending the allergen information on cosmetic products as it claims to have seen only up to 100 individual cases worldwide in the last several decades who have reported irritation or allergic reactions to galaxolide through the use of cosmetic products. Galaxolide has been reported to be found in human biomonitoring studies and its presence in human tissue has been evaluated by several scientific authorities. For example, Galaxolide was detected in 97% of breast milk samples in mothers from Massachusetts in a 2004 study. A 2009 study detected Galaxolide in the blood plasma of 91% of the study participants. Extensive investigations into the presence of galaxolide in biomonitoring studies, have been completed and evaluated by various regulatory authorities. The outcome of all those studies is that galaxolide is safe for use in consumer products.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Galaxolide

Start with the simplest possible case. Write down what Galaxolide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Galaxolide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Galaxolide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Galaxolide

In research: Galaxolide appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Galaxolide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Galaxolide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cyclopentanes, Heterocyclic compounds with 3 rings, Isochromenes, so understanding it makes those chapters shorter.
In everyday life: Look for Galaxolide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Galaxolide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Galaxolide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Galaxolide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Galaxolide in simple terms?

Why does Galaxolide matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Galaxolide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Galaxolide.