A geminal diether (R¹ = H). Ketals, considered a subclass of acetals, are also geminal diethers (R¹ = C, aliphatic or aromatic). Acetals are (1) independent structural units or a part of certain biological and commercial polymers, (2) blocking or protecting groups for complex molecules undergoing selective synthetic transformations, and (3) entry compounds for independent organic chemical reactions.

A common medicine used to relieve mild to moderate pain and reduce fever. Acetaminophen (N-acetyl-p-aminophenol), or paracetamol, is a white crystalline compound with the molecular formula C₈H₉NO₂ (Fig. 1). It is a member of the aniline family of analgesics (acting to relieve pain) and antipyretics (acting to prevent or reduce fever). Three types of nonopioid analgesics exist: aniline derivatives (such as acetaminophen), nonsteroid anti-inflammatory drugs (NSAIDs, such as aspirin, ibuprofen, and naproxen sodium), and nonacidic pyrazole derivatives (such as phenylbutazone and dipyrone). NSAIDs and pyrazole drugs are both used to relieve pain, reduce fever, and reduce inflammation, while pyrazole drugs can also be used for their spasmolytic (acting to relieve muscle spasms) properties. Aniline derivatives exhibit analgesic and antipyretic, but not anti-inflammatory, properties. See also: Analgesic; Aspirin; Fever; Inflammation; Medicine; Pain; Pharmacology; Pharmacy

A colorless organic acid, CH₃COOH, with a pungent odor and sour taste. Acetic acid (see figure) is the principle component of vinegar. Concentrated acid is called glacial acetic acid because of its readiness to crystallize at cool temperatures. See also: Acid and base; Organic chemistry; Vinegar

A chemical compound, (CH₃)₂CO; the first member of the homologous series of aliphatic ketones. Acetone (see illustration) is a colorless, volatile, and flammable liquid. Acetone occurs naturally in plants and animals. Its physical properties include boiling point 56.2°C, melting point −94.8°C, and specific gravity 0.791. Acetone is an extremely important, low-cost raw material that is used for production of other chemicals. See also: Ketone

An organic compound with the formula C₂H₂ or HCCH. The first member of the alkynes, acetylene is a gas with a narrow liquid range; the triple point is −81°C (−114°F). The heat of formation (ΔH°_f) is +227 kilojoules/mole, and acetylene is the most endothermic compound per carbon of any hydrocarbon. The compound is thus extremely energy-rich and can decompose with explosive force. At one time acetylene was a basic compound for much chemical manufacturing. It is highly reactive and is a versatile source of other reactive compounds.

One of an important class of reactive organic compounds derived from acids via formal intermolecular dehydration; thus, acetic acid (1), on loss of water, forms acetic anhydride (2).

One of a large group of organic substances possessing the halocarbonyl group

An explosive, poisonous, flammable liquid, boiling at 77.3°C (171°F), partly soluble in water. The formula CH₂ CH C N indicates it may be regarded as vinyl cyanide, and its systematic name is 2-propenonitrile. Acrylonitrile is prepared by ammoxidation of propylene, according to the reaction below, over various

A process in which a hydrogen atom in an organic compound is replaced by an acyl group (RCO where R = an organic group). The reaction involves substitution by a nucleophile (electron donor) at the electrophilic carbonyl group (CO) of a carboxylic acid derivative. The substitution usually proceeds by an addition-elimination sequence [reaction]. Two common reagents, with the general formula RCOX, that bring about acylation are acid halides (X = Cl,Br) and anhydrides (X = OCOR). There are also other acylating reagents. The carboxylic acid (X = OH) itself can function as an acylating agent when it is protonated by a strong acid catalyst as in the direct esterification of an alcohol. Typical nucleophiles in the acylation reaction are alcohols (ROH) or phenols (ArOH), both of which give rise to esters, and ammonia or amines (RNH₂), which give amides. See also: Acid anhydride; Acid halide; Amide; Amine; Electrophilic and nucleophilic reagents

A material capable of fastening together two other materials by means of surface attachment. Terms such as glue, mucilage, mastic, and cement can be synonymous with the term "adhesive." In a generic sense, an adhesive is any material capable of fastening by means of surface attachment (see figure), and thus includes inorganic materials such as portland cement and solder. Practically, however, adhesives are a broad set of materials composed of organic, primarily polymeric materials that can be used to fasten two other materials together. The materials being fastened are often called adherends, and the resulting assembly is called an adhesive joint or adhesive bond. See also: Adhesive bonding; Cement