278:
57:
130:
radicalyzes to monatomic bromine. These bromine atoms add to an alkene at the most accessible site, to give a bromoalkyl radical, with the radical on the more substituted carbon. That radical then abstracts a hydrogen atom from another HBr molecule to regenerate the monatomic bromine and continue
195:
In the case of silicon, germanium, or phosphorus, the energetics are unfavorable unless the heavy atom bears a pendant hydrogen. Other electronegative substituents on silicon appear to reduce the barrier.
149:
is a valuable synthetic technique for anti-Markovnikov carbon substitution, but free-radical addition does not occur with the other hydrohalic acids. Radical formation from HF, HCl, or HI is extremely
533:
Stacey, F. W.; Harris, J. F., Jr. (30 April 2004). "Formation of carbon-hetero atom bonds by free-radical chain additions to carbon-carbon multiple bonds". In
Denmark, Scott E. (ed.).
100:
precursor to give a radical with lesser bond order. In the other, the newly-formed radical product abstracts another substituent from the adding reagent to regenerate the adding radical.
157:
The behavior of hydrogen bromide generalizes in two separate directions. Halogenated compounds with a relatively stable radical can dissociate from the halogen. Thus, for example,
48:
into radicals, which then induce further decomposition in their compatriots before recombination. Different mechanisms typically apply to reagents without such a weak bond.
485:
Kharasch, M. S.; Mayo, Frank R. (1933). "The
Peroxide Effect in the Addition of Reagents to Unsaturated Compounds. I. The Addition of Hydrogen Bromide to Allyl Bromide".
609:
168:
Separately, unsubsituted compounds with a relative stable radical can dissociate from hydrogen. In general, these reactions risk polymerized byproducts (see
154:
and chemically disfavored. Hydrogen bromide is incredibly selective as a reagent, and does not produce detectable quantities of polymeric byproducts.
552:
821:
698:
655:
242:
962:
602:
470:
37:. Radical additions are known for a variety of unsaturated substrates, both olefinic or aromatic and with or without heteroatoms.
188:
add across a double bond. But if the unsaturated substrate polymerizes easily, they catalyze polymerization instead. In thermal
1061:
870:
865:
675:
1030:
1035:
1066:
595:
237:, bonds between arenes and their substituents are (in)famously strong. Radical reactions with arenes typically present
1056:
340:
277:
1000:
690:
165:, and other sulfur halides can add radically to give respectively β‑halo sulfones, sulfoxides, or sulfides.
727:
627:
572:
Dreessen, Tim; Jargstorff, Christian; Lietzau, Lars; Plath, Christian; Stademann, Arne; and Wille, Uta (2004). "
415:
368:
957:
96:
In a free-radical addition, there are two chain propagation steps. In one, the adding radical attaches to a
1005:
806:
306:
238:
760:
410:
352:
266:
990:
922:
770:
230:
45:
112:
108:
985:
713:
405:
245:, because generating the aryl radical requires a strong (radical) leaving group. One example is the
224:
200:
199:
Although nitrogen oxides naturally radicalize, careful control of the radical species is difficult.
995:
927:
912:
855:
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386:
309:
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56:
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790:
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30:
22:
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in a reagent. Under reaction conditions (typically heat or light), some weak bonds
932:
738:
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635:
234:
34:
265:
between the two propagation steps. In general, radical additions can also start
891:
826:
544:
458:
348:
151:
433:
L.G. Wade's
Organic Chemistry 5th Ed. (p 319) – Mechanism supplements original.
312:. This reaction is not catalytic, and requires the oxidized radical source in
336:
942:
587:
181:
119:
called the "peroxide effect". Reaction is slower with alkynes than alkenes.
107:(typically, least substituted) carbon; the radical then stabilizes on the
390:
498:
382:
332:
317:
189:
86:: A radical reacts with a non-radical to produce a new radical species
372:
344:
302:
298:
258:
92:: Two radicals react with each other to create a non-radical species
328:
845:
177:
463:
Advanced
Organic Chemistry: Reactions, Mechanisms, and Structure
591:
69:
The basic steps in any free-radical process (the radical chain
665:
192:
additions, telomerization usually proceeds to about 6 units.
40:
Free-radical reactions depend on one or more relatively weak
103:
In general, the adding radical attacks the alkene at the
16:
Organic addition reaction which involves free radicals
80:: A radical is created from a non-radical precursor.
971:
905:
879:
835:
799:
751:
712:
689:
626:
574:Self-Terminating, Oxidative Radical Cyclizations
291:self-terminating oxidative radical cyclization
283:Self-terminating oxidative radical cyclization
603:
123:
8:
316:amounts. In effect, the radical species is
610:
596:
588:
568:
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564:
528:
353:abstracts an intramolecular hydrogen atom
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524:
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520:
518:
516:
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487:Journal of the American Chemical Society
276:
55:
453:
451:
449:
447:
445:
443:
441:
439:
426:
636:Unimolecular nucleophilic substitution
111:carbon. The result is typically anti-
646:Bimolecular nucleophilic substitution
7:
699:Electrophilic aromatic substitution
257:A radical addition which leaves an
169:
666:Nucleophilic internal substitution
656:Nucleophilic aromatic substitution
393:radicals show similar reactivity.
243:nucleophilic aromatic substitution
14:
582:, issue 9, pp. 480–497.
465:(4th ed.), New York: Wiley,
822:Lindemann–Hinshelwood mechanism
871:Outer sphere electron transfer
866:Inner sphere electron transfer
676:Nucleophilic acyl substitution
401:The other radical reactions:
273:With stable inorganic radicals
1:
1036:Diffusion-controlled reaction
207:dinitro compound, but also a
351:radical. The vinyl radical
347:to generate a very reactive
135:Compounds that add radically
52:Mechanism and regiochemistry
691:Electrophilic substitutions
545:10.1002/0471264180.or013.04
1083:
1001:Energy profile (chemistry)
963:More O'Ferrall–Jencks plot
628:Nucleophilic substitutions
222:
203:adds to give a mixture: a
138:
105:most sterically accessible
1031:Michaelis–Menten kinetics
416:free-radical halogenation
958:Potential energy surface
837:Electron/Proton transfer
722:Unimolecular elimination
329:the paradigmatic example
318:synthetically equivalent
172:). For example, in the
124:the paradigmatic example
62:Radical hydrobromination
1006:Transition state theory
807:Intramolecular reaction
733:Bimolecular elimination
375:and the stable radical
115:addition, a phenomenon
1062:Free radical reactions
800:Unimolecular reactions
761:Electrophilic addition
411:radical polymerization
341:ceric ammonium nitrate
286:
267:radical polymerization
66:
991:Rate-determining step
923:Reactive intermediate
781:Free-radical addition
771:Nucleophilic addition
714:Elimination reactions
539:(1 ed.). Wiley.
280:
170:§ Side reactions
59:
27:free-radical addition
986:Equilibrium constant
406:radical substitution
355:5 atoms away before
261:product can undergo
225:Radical substitution
201:Dinitrogen tetroxide
145:Radical addition of
1067:Reaction mechanisms
996:Reaction coordinate
928:Radical (chemistry)
913:Elementary reaction
856:Grotthuss mechanism
620:reaction mechanisms
499:10.1021/ja01333a041
387:ammonium persulfate
349:vinyl nitrate ester
310:radical cyclization
263:radical cyclization
1057:Addition reactions
1021:Arrhenius equation
791:Oxidative addition
753:Addition reactions
361:-trig ring-closure
287:
247:Meerwein arylation
239:retrosynthetically
229:Although aromatic
174:thiol-ene reaction
78:Radical initiation
67:
1044:
1043:
1016:Activated complex
1011:Activation energy
973:Chemical kinetics
918:Reaction dynamics
817:Photodissociation
554:978-0-471-26418-7
536:Organic Reactions
367:radical can then
363:. The resulting
297:radicals oxidize
209:nitro substituent
141:Hydrohalogenation
90:Chain termination
84:Chain propagation
31:addition reaction
23:organic chemistry
1074:
948:Collision theory
897:Matrix isolation
851:Harpoon reaction
728:E1cB-elimination
612:
605:
598:
589:
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570:
559:
558:
530:
503:
502:
493:(6): 2468–2496.
482:
476:
475:
455:
434:
431:
377:nitrogen dioxide
322:monatomic oxygen
285:
284:
241:as instances of
219:To aryl radicals
186:hydrogen sulfide
147:hydrogen bromide
128:hydrogen bromide
109:more substituted
64:
63:
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1081:
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1072:
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1026:Eyring equation
967:
938:Stereochemistry
901:
887:Solvent effects
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275:
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227:
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143:
137:
117:Morris Kharasch
98:multiply-bonded
73:) divide into:
61:
60:
54:
33:which involves
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12:
11:
5:
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906:Related topics
903:
902:
900:
899:
894:
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880:Medium effects
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560:
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504:
477:
471:
435:
425:
423:
420:
419:
418:
413:
408:
398:
395:
335:radical (from
314:stoichiometric
307:intramolecular
274:
271:
254:
253:Side reactions
251:
220:
217:
211:adjacent to a
136:
133:
131:the reaction.
94:
93:
87:
81:
53:
50:
15:
13:
10:
9:
6:
4:
3:
2:
1079:
1068:
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1029:
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1024:
1022:
1019:
1017:
1014:
1012:
1009:
1007:
1004:
1002:
999:
997:
994:
992:
989:
987:
984:
982:
981:Rate equation
979:
978:
976:
974:
970:
964:
961:
959:
956:
954:
953:Arrow pushing
951:
949:
946:
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941:
939:
936:
934:
931:
929:
926:
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919:
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908:
904:
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895:
893:
890:
888:
885:
884:
882:
878:
872:
869:
867:
864:
862:
861:Marcus theory
859:
857:
854:
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849:
847:
844:
843:
841:
838:
834:
828:
825:
823:
820:
818:
815:
813:
812:Isomerization
810:
808:
805:
804:
802:
798:
792:
789:
787:
786:Cycloaddition
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772:
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759:
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521:
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478:
474:
472:0-471-60180-2
468:
464:
460:
454:
452:
450:
448:
446:
444:
442:
440:
436:
430:
427:
421:
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409:
407:
404:
403:
402:
396:
394:
392:
388:
384:
380:
378:
374:
370:
366:
365:alkyl nitrate
362:
360:
354:
350:
346:
343:) adds to an
342:
338:
334:
330:
325:
323:
319:
315:
311:
308:
304:
300:
296:
292:
279:
272:
270:
268:
264:
260:
252:
250:
248:
244:
240:
236:
235:aryl radicals
232:
226:
218:
216:
214:
213:nitrite ester
210:
206:
202:
197:
193:
191:
187:
183:
179:
175:
171:
166:
164:
160:
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148:
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79:
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75:
74:
72:
58:
51:
49:
47:
43:
38:
36:
35:free radicals
32:
28:
24:
19:
933:Molecularity
780:
578:
535:
490:
486:
480:
462:
459:March, Jerry
429:
400:
381:
358:
326:
290:
288:
256:
228:
198:
194:
167:
156:
144:
121:
102:
95:
68:
65:of an alkene
39:
26:
20:
18:
892:Cage effect
827:RRKM theory
743:elimination
305:through an
269:processes.
259:unsaturated
233:stabilizes
152:endothermic
113:Markovnikov
1051:Categories
422:References
337:photolysis
223:See also:
182:disulfides
139:See also:
943:Catalysis
839:reactions
579:Molecules
295:inorganic
231:resonance
71:mechanism
461:(1992),
397:See also
391:hydroxyl
369:fragment
163:sulfenyl
159:sulfonyl
46:homolyse
383:Sulfate
333:nitrate
303:ketones
299:alkynes
205:vicinal
618:Basic
551:
469:
389:) and
385:(from
373:ketone
345:alkyne
190:silane
184:, and
178:thiols
29:is an
846:Redox
682:Acyl)
371:to a
42:bonds
735:(E2)
724:(E1)
576:".
549:ISBN
467:ISBN
331:, a
705:Ar)
662:Ar)
541:doi
495:doi
359:exo
339:of
327:In
320:to
301:to
289:In
122:In
21:In
1053::
773:(A
763:(A
701:(S
678:(S
672:i)
668:(S
658:(S
652:2)
648:(S
642:1)
638:(S
563:^
547:.
507:^
491:55
489:.
438:^
379:.
357:5-
324:.
293:,
249:.
215:.
180:,
176:,
161:,
126:,
25:,
777:)
775:N
767:)
765:E
741:i
739:E
703:E
680:N
670:N
660:N
650:N
640:N
611:e
604:t
597:v
557:.
543::
501:.
497::
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
