Alkyl ketene dimers (AKDs) are a family of organic compounds based on the 4-membered ring system of oxetan-2-one, which is also the central structural element of propiolactone and diketene. Attached to the oxetane ring of technically relevant alkyl ketene dimers there is a C12 – C16 alkyl group in the 3-position and a C13 – C17 alkylidene group in the 4-position.
The main application of alkylated ketene dimers is in the sizing of paper and cardboard, as well as in the hydrophobation of cellulose fibers. The products thus modified are distinguished by higher mechanical strengths and less penetration of water, inks or printing inks.[1]
AKD's feature hydrophobic alkyl groups extending from a beta-propiolactone ring. A specific example is derived from the dimerization of the ketene of stearic acid. This ketene is generated by pyrolysis of stearoyl chloride.[2] AKD's react with the hydroxyl groups on the cellulose via esterification reaction. The esterification is competitive with hydrolysis of the AKD. Prior to the development of AKD's, hydrophobicity was imparted by incorporating rosin into the paper.[3]
Related to AKDs, is alkenylsuccinic anhydride (ASA). As for AKDs, ASA reacts with hydroxy groups of the cellulose to form an ester, anchoring the hydrophobic group to the surface. ASA is prepared by the ene reaction of unsaturated hydrocarbons with maleic anhydride.[4]
^"AKD, Alkylketene Dimer".
^Raimund Miller, Claudio Abaecherli, Adel Said, Barry Jackson "Ketenes" in Ullmann's Encyclopedia of Industrial Chemistry, 2001, Wiley-VCH, Weinheim. doi:10.1002/14356007.a15_063
^Werner J. Auhorn "Paper and Board, 3. Chemical Additives" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim. 2012. doi:10.1002/14356007.o18_o11
Alkylketenedimers (AKDs) are a family of organic compounds based on the 4-membered ring system of oxetan-2-one, which is also the central structural...
propiolactones. A specific example is the dimerization of the ketene of stearic acid to afford alkylketenedimers, which are widely used in the paper industry. AKD's...
for alkylketenedimers. In the United States alkenylsuccinic anhydrides are the preferred paper sizing agents, whereas in Europe, alkylketenedimers (AKDs)...
chemistry had to switch to a neutral process. At several places AKD (alkylketenedimer) and ASA (alkenyl succinic anhydride) are used. Latest development...
internal sizing chemicals used in papermaking at the wet end are alkylketenedimer (AKD) and alkyl succinic anhydride (ASA) in neutral pH conditions, and the...
internal (beater added) sizing provided by rosin, alkyl succinic anhydride (ASA), or alkylketenedimer (AKD) and surface sizing provided by starch. A sheet...
classification symbol: Cargo ship dock (AKD) Akpet language (ISO 639: akd) Alkylketenedimer; see Wet strength Avian keratin disorder, a disorder involving deformities...
generation of phenyl-substituted methylene ketene from a Meldrum's acid derivative and hot methanol vapor. Other alkyl substitutions can also lead to β,γ-unsaturated...
to form stabilized dimers through hydrogen bonds. For boiling to occur, either the dimer bonds must be broken or the entire dimer arrangement must be...
The main process involves dehydration of acetic acid to give ketene at 700–750 °C. Ketene is thereafter reacted with acetic acid to obtain the anhydride:...
are also applied, including alkenyl succinic anhydride (ASA) and alkylketenedimers (AKD). Cationic starch increases strength because it binds to the...
popular for laboratory scale reactions. In the Kolbe nitrile synthesis, alkyl halides undergo nucleophilic aliphatic substitution with alkali metal cyanides...
conversion of a ketene into an allene: Attempted synthesis of "titanocene", i.e. Ti(C5H5)2, produces a fulvalene complex. The titanocene dimer was recognised...
Nitrosoarenes typically participate in a monomer–dimer equilibrium. The azobenzene N,N'-dioxide (Ar(–O)N+=+N(O–)Ar) dimers, which are often pale yellow, are generally...
chemistry, the acyl group (IUPAC name alkanoyl if the organyl group is alkyl) is usually derived from a carboxylic acid, in which case it has the formula...
reacted with potassium hydroxide the reaction product is the 1,2-dinitro dimer. Chloramphenicol is a rare example of a naturally occurring nitro compound...
double-bond resonance structures) breaks. For example, when one substituent is alkyl and another aryl, the aryl-substituted carbon is usually released as a carbene...
rubber. Transition-metal allyl complexes, such as allylpalladium chloride dimer Wikiquote has quotations related to Allyl group. Allylic strain Carroll...
smaller scale, ethyltoluene, ethylanilines, 1,4-hexadiene, and aluminium alkyls. Products of these intermediates include polystyrene, unsaturated polyesters...
molecule, granting it stability. There is also evidence for the asymmetric red dimer O=N–O=N when nitric oxide is condensed with polar molecules. It reacts with...
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