What functional group does acetaldehyde have?

The functional group is an aldehyde, written -CHO

MeSH defines aldehydes as organic compounds containing a carbonyl group in the form -CHO. ChEBI defines an aldehyde as a compound RC(=O)H, in which a carbonyl group is bonded to one hydrogen atom and to one R group. The R group is the rest of the molecule. The functional group is the -CHO piece.

In acetaldehyde, that R group is a methyl group, CH3. ChEBI writes the structure as [H]C(C)=O, which puts the hydrogen on the carbonyl carbon in the formula. PubChem's connectivity SMILES for the same compound is CC=O. The double bond to oxygen is the carbonyl. The hydrogen required by the aldehyde definition is the H in -CHO.

Sources: Aldehydes: MeSH scope note; aldehyde (CHEBI:17478); acetaldehyde (CHEBI:15343); Acetaldehyde (CID 177)

Acetaldehyde is one aldehyde, not the name of the group

ChEBI describes acetaldehyde as the aldehyde formed from acetic acid by reduction of the carboxy group. PubChem compound 177 lists the molecular formula C2H4O, a molecular weight of 44.05, and the IUPAC name acetaldehyde. NIAAA writes that same metabolite as CH3CHO when it describes alcohol breakdown.

Those records are three views of one structure: two carbons, four hydrogens, and one oxygen, with the oxygen double-bonded to the end carbon that also carries a hydrogen. MeSH calls acetaldehyde a colorless, flammable liquid used in the manufacture of acetic acid, perfumes, and flavors, and an intermediate in the metabolism of alcohol. The manufacturing use and the metabolite are the same compound. They are not two functional groups.

Sources: acetaldehyde (CHEBI:15343); Acetaldehyde (CID 177); How the body metabolizes alcohol; Acetaldehyde: MeSH scope note

Ethanol is an alcohol; acetaldehyde is the aldehyde after it

NIAAA names the alcohol in drinks ethanol and writes it CH3CH2OH. Most of that ethanol is broken down in the liver. Alcohol dehydrogenase (ADH) transforms ethanol into acetaldehyde (CH3CHO). Aldehyde dehydrogenase (ALDH) then breaks acetaldehyde down to acetate (CH3COO-), which is broken down to carbon dioxide and water, mainly in tissues other than the liver.

The oxygen moves from a hydroxyl group, the -OH in ethanol, to a carbonyl, the C=O in acetaldehyde. That carbonyl carbon is also bonded to a hydrogen, which is what makes the group an aldehyde under the ChEBI and MeSH definitions above. Acetate is the next product NIAAA names. It is not a second name for acetaldehyde.

The metabolite story, including why one molecule does not explain a next morning, stays on what is acetaldehyde. The enzyme order stays on alcohol metabolism. This page stops at the functional group.

Sources: How the body metabolizes alcohol; aldehyde (CHEBI:17478); Aldehydes: MeSH scope note

Ethanal, acetic aldehyde, and the CAS number

PubChem lists ethanal, acetic aldehyde, ethyl aldehyde, and 75-07-0 among the synonyms for acetaldehyde. Ethanal is a systematic name built on the same ethan- stem as ethanol, with the ending that marks an aldehyde. Acetic aldehyde and ethyl aldehyde are older names that still appear on reference records.

A synonym is not a different functional group. If a paper or a label uses one of those names, the formula C2H4O or the registry number 75-07-0 is the check that it is this compound. PubChem also lists CH3CHO itself as a synonym, which matches the structure NIAAA prints.

Sources: Acetaldehyde (CID 177); How the body metabolizes alcohol

How to pronounce acetaldehyde

Merriam-Webster's pronunciation spelling is ˌa-sə-ˈtal-də-ˌhīd. The stressed syllable is tal. The medical entry on the same page uses ˌas-ə-ˈtal-də-ˌhīd. The dictionary defines the word as a colorless volatile water-soluble liquid aldehyde, formula C2H4O, used chiefly in organic synthesis.

It records the first known use in 1857 and traces the English word to German Acetaldehyd, from acet- plus Aldehyd, aldehyde. The pronunciation entry does not describe alcohol metabolism. It tells you how the dictionary says the name.

Sources: acetaldehyde

What the functional group does not decide

On its metabolism page, NIAAA calls acetaldehyde a highly toxic substance and a known carcinogen, and says it is generally short-lived because ALDH converts it to acetate. The hangover fact sheet calls it a toxic, short-lived byproduct of alcohol metabolism, primarily by the liver. Those sentences describe the metabolite. They are not a symptom score, and a structure diagram is not protection from drinking.

The same hangover sheet says there is no cure for a hangover other than time, and that coffee, a shower, or a morning drink will not cure one. A functional-group name will not either. Questions about how long alcohol remains are on how long alcohol stays in your system.

• The -CHO group names the chemistry. It does not measure impairment.
• CH3CHO and C2H4O refer to the same compound on the sources above.
• Ethanol's -OH group is a hydroxyl, not an aldehyde.

Sources: How the body metabolizes alcohol; Hangovers: causes, remedies, and safety

Where Joyrise fits, and where it does not

A structure diagram is not a serving direction. Joyrise is an Alcohol Metabolizing Aid: a DHM supplement built around dihydromyricetin. The capsule label says to take 3 capsules while consuming alcohol, or before bed. Do not exceed 3 servings (9 capsules) per day. Much of the alcohol-related DHM evidence is preclinical, and Joyrise does not lower BAC, reverse impairment, or make driving safe. Read the full directions and warnings on our Alcohol Metabolizing Aid capsules page before you buy.

Sources: Joyrise capsules: product page and current label; Shen et al., 2012: DHM and alcohol-related signaling