Alkynes and Compounds Containing C≡C Groups

7/30/2019 Alkynes and Compounds Containing CC Groups

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C H A P T E R 5

Alkynes and Com poundsContaining C--C GroupsTerminal C--CH1-HalopropynesPhenylacetylene in Various Solut ions1,4-DiphenylbutadiynePropargyl Alcohol vs Propargyl Fluoride1,3-DihalopropynesPheny lace ty lene and Pheny lace ty lene- ldReferences

9395969798989999

Figures TablesFigure 5-1 100 (95) Table 8-1 106 (93)Figure 5-2 101 (96) Table 5-2 107 (94)Figure 5-3 101 (97) Table 5-3 108 (94)Figure 5-4 102 (97) Table 5-4 109 (95)Figure 5-5 102 (97) Table 5-4a 109 (95)Figure 5-6 103 (98) Table 5-5 109 (97)Figure 5-7 104 (98) Table 5-6 110 (97, 98)Figure 5-8 105 (99) Table 5-7 111 (98)

Table 5-8 112 (98)Table 5-9 113 (99)

*Numbers in parentheses indicate in-text page reference.

TERMINAL C=CHT a b le 5 .1 l i st s IR d a ta a n d a s s i g n m e n t s f o r c o m p o u n d s c o n t a i n i n g t h e t e r m i n a l a c e t y l e ni c g r o u p(1) . The v - -C -H m o d e o c c u r s n e a r 3 3 0 0 c m - 1 w i t h a w e a k s h o u l d e r o n t h e l o w f r e q u e n c y s i d eo f t h e s t ro n g I R b a n d . T h i s w e a k s h o u l d e r h a s b e e n a t t r i b u t e d t o a F e r m i r e s o n a n c e i n t e r a c t i o nw i t h v----C-H a n d th e c o m b i n a t i o n t o n e v C - C + 2 [ C - - - -C - H b e n d i n g ] ( 1 ).A l l o f t h e s e c o m p o u n d s e x h i b i t v C - C i n t he r e g i o n 2 1 0 0 - 2 1 4 8 c m - 1 , a n d t h i s b a n d i s w e a ki n m o s t c as e s. C o m p o u n d s w h e r e t h e h a l o g e n a t o m o r a c a r b o n y l g r o u p i s j o i n e d t o th e t e r m i n a la c e t y l e n i c g r o u p e x h i b i t s t r o n g I R v c - - c a b s o r p t i o n b a n d s .

A w e a k I R b a n d i n t h e re g i on 8 9 7 - 9 6 1 c m - 1 is as s ig n e d to v C - C . T h e - - C - H b e n d i n g m o d ei s n o t s p l i t i n t h e c a s e o f 1 - a lk y n e s , a n d o c c u r s i n t h e r e g i o n 6 2 8 - 6 3 3 c m - 1 . Su b s t i t u t i o n o f a

93


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9 4 Alkynes and Compounds Containing C=C Groupsha logen a tom on the 3 -ca rbon a tom s p l i t s the degeneracy and bo th in -p lane and ou t -o f -p lane- -=C-H bend ing m odes a r e obs e rved in the IR . W i th the excep t ion o f 3 - iod opro pyne the in -p laneb e n d i n g m o d e o c c u r s a t a h i g h e r f r e q u e n c y t h a n t h e o u t - o f - p la n e b e n d i n g m o d e s . F o r e x a m p l e ,3 - iodo propy ne exh ib i t s the C - H ben d ing mo des a t 637 cm -1 , wh i le the C1, Br, and F ana logsexh ib i t the in -p lane ben d ing mo de a t 652 , 649 , and 674 cm -1 , r e s pec t ive ly, and the ou t -o f -p lanebend ing m ode occur s a t 637, 639 , and 63 6c m -1 , r e s pec tive ly (2 ).S ubs t i tu t ion o f deu te r ium fo r hyd roge n - -=C-H to - -- -C-D he lps in es tab l i s h ing the funda-men ta l v ib ra t ions tha t r e s u l t f rom th i s po r t io n o f the molecu le . In the cas e o f 3 -ch lo ro propy ne-1-da n d 3 - b r o m o p r o p y n e - l - d t h e v = C - D m o d e s o c c u r a t 26 1 8 a n d 2 6 0 7 c m - 1 , re s p e ct i ve l y ( se eTab le 5 .2 ) . I n the cas e o f = C - D bend ing , the C1 and Br ana logs exh ib i t the in -p lane mod e a t 516and 51 2c m -1 , r es pec tive ly , wh i le the ou t -o f -p lane m ode occur s a t 502 a nd 50 3c m -1 , r e s pec-tively.

T h e 3 - c h l o r o p r o p y n e - l - d , 3 - b r o m o p r o p y n e - l - d , a n d p h e n y l a c e t y l e n e - l - d a r e i n t e r e s t i n gbecaus e the i r v=- -C-D and vC-=C mod es coup le . The vC=- -C mo de s h i f ts f rom 2147 to 2000 ,2138 to 2006 , and 2119 to 198 9cm -1 fo r 3 -C1 , Br, and 2 -phen y l C- -=C-H and D ana logs ,r es pec t ive ly . On the o the r hand , the v_=C-H mode and v_=C-D modes a r e (3325 and 2618) ,( 3 3 15 a n d 2 6 0 7 ) , a n d ( 3 3 1 5 a n d 2 5 9 6 c m - 1 ) f o r t h e 3- C 1 , 3 - Br a n d 2 - p h e n y l C ~ C - H a n d Danalogs , respect ively . The ra t io of v=C-H/v=_C-D is 1.27, 1.28, and 1.28, respectively, and, ifv = C - D were a pu re v ib ra t ion i t wou ld be expec ted to occur a t 2340 cm -~ . Becaus e vC--=C s h i ft st o l o w e r f r eq u e n c y u p o n D s u b s t it u t i o n t o g e t h e r w i t h t h e b e h a v i o r o f v C - D , t h e ir f r e q u e n c ybehav io r i s expec ted when the two modes a r e coup led . As vC=C and v=- -C-H occura p p r o x i m a t e l y 1 1 7 0 c m - a a p a rt , t h e a m o u n t o f c o u p l i n g b e t w e e n t h e se t w o m o d e s i s m o s tl ikely negl ig ible (3-5) .

T e r m i n al a c et y le n i c c o m p o u n d s o f te n e x h i b it t h e f ir st o v e rt o n e o f = C - H b e n d i n g i n t h ereg ion 1219 -1265 cm -1 , and fo r the D ana logs nea r 1000 -1043 cm -1 . In add i t ion , the C -C -= Cbend ing m ode i s obs e rved in the r eg ion 300 -353 cm -1 (1 ) .

Tab le 5 . 2 l i s t s the 15 v ib ra t iona l a s s ignmen ts fo r 3 -ha lop ropynes us ing bo th IR and Ramand a ta ( 2 ,4 , 5) . T h e v C - H a n d v C - D a n d v C = C m o d e s h a v e b e e n p r e v i o u sl y d i sc u s se d . T h ev ib ra t ions mos t a f f ec ted by change in the ha logen a tom fo r the CH2X group a re vC-X s ke le ta lbend ing , CH2 wagg ing , CH2 tw is t ing , and CH2 rock ing . In mos t cas es thes e fundamen ta l sdecreas e in f r equency p rogres s ing in the s e r ie s F to I . Thes e m olecu les h ave a p lane o f s ymm et ry ,and the 10 v ib ra t ions tha t occu r w i th in the p lane a r e des igna ted as a ' f undamen ta l s and the 5v ib ra t ions tha t occu r ou t -o f - the p lane a r e des igna ted as a" fundamen ta l s . Thes e molecu les haveCs s ymmet ry .

Table 5 .3 l ists IR vap or phas e data an d ass ig nm ents for 1-alkynes (3) . Most of theseas s ignmen ts a r e fo r the a lky l g roup o f thes e 1 -a lkynes . The number s in pa ren thes i s a r e themeas ured abs o rbances , and s tudy o f thes e number s s hows the in tens i t i e s r e la t ive to one ano the rin each s pec t rum. I t i s o f in te r es t to no te tha t the r a tio [ (A)CCH ben d / (A )vas ym . CH2] dec reas esas the number o f (CH2) , inc reas es f rom 2 to 10 . Th i s ind ica tes tha t the in tens i ty fo r CCHbend ing i s e s s en t i a l ly cons tan t and the in tens i ty fo r vas ym. (CH2) , becomes more in tens e as nbecom es l a rge r . It s hou ld be no ted tha t vas ym. (CH2) , s h i ft s to lower f r eq uency by 17 cm -1 as ni s inc reas ed f rom 2 to 10 . Mos t l ike ly the d ipo le moment change du r ing vas ym. CH2 changess l ight ly with th is small sh if t in i ts f requency.


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Variables in Data Interpretation 95F igure 5 .1 s hows a p lo t o f abs o rbance r a t io s fo r the 1 -a lkynes vs the num ber o f ca rbon a tom s

in the 1 -a lkynes (3 ) . Cor re la t ions s uch as thes e he lp in s pec t r a - s t ruc tu re iden t i f i ca t ion o fu n k n o w n s am p l es .

1 - H A L O P R O P Y N E S1-Halopropynes have C3v s ymm et ry , and the 15 fundam en ta l s a r e d i st r ibu ted : 5aa, and 5e (The efundam en ta l s a r e doub ly degenera te ) . The a l m odes s h ou ld y ie ld pa ra l l e l IR vapor band s andp o l a ri z e d R a m a n b a n d s w h i l e t h e e m o d e s s h o u l d y i e l d p e r p e n d i c u l a r I R v a p o r b a n d s a n ddepo la r ized Raman bands . V ib ra t iona l a s s ignmen ts in Tab le 5 . 4 were made us ing thes e c r i t e r i a(7).

I t has a l ready been no ted tha t v = C - D and vC_=C coup led cons ide rab ly in the case o f the 1 -h a l o p r o p y n es . D u r i n g a c y cl e o f v C = C , b o t h t h e C - C a n d C - X b o n d s m u s t e x p a n d a n dcontract .

H3 C +-- C~ C ~ X +-~ H3 C --+ C~ C +-- XT h e r ef o re , th i s c o m p l e x v C _= C m o d e m u s t i n c lu d e c o n t r i b u t i o n f r o m b o t h v C - C a n d v C - X . Acompar i s on o f thes e modes vs thos e fo r p ropyne a re p res en ted he re :

vC--C vC- C vC- X or vC- H1-halopropyne cm- 1 cm- 1 cm- 1Br 2239 1037 465I 2210 1013 403propyne 2130 930 3320

I t i s no ted tha t vC-=C fo r 1 -ha lo p ropynes occur s ap prox im ate ly 95 cm -1 h ig her in f r equencythan i t occu r s fo r p ropyn e . In add i t ion , vC -C fo r 1 -ha lop ropyne s occur s approx imate ly 90 cm -1h i g h e r i n f re q u e n c y t h a n i t o c c u rs f o r p r o p y n e . T h e v C - X m o d e o c c u r s a t l o w e r f r e q u en c y t h a nthe o the r two v ib ra t ions wh i le v C -H occur s a t h igher f requency. Moreover , the fo rce cons tan tfor Br is h igh er th an i t is for I. Al l of these facts sugg es t that the vC = C m od e for 1 -halo prop yne iscomplex and invo lves a s t r e tch ing mot ion o f the two ad jacen t g roups .

Tab le 5 . 4a l i s t s the Cor io l i s coup l ing cons tan t s fo r 1 -ha lop ropyne (7 , 8 ) , p ropyne (9 ) andpropyne- l -d (10 ) . Thes e Cor io l i s cons tan t coup l ing coef f i c ien t s a r e inc luded s o tha t the r eaderhas be t t e r knowledge abou t in te rp re t ing s pec t r a l da ta . Lord and Mer r i f i e ld (11 ) have s t a ted tha tthe phys ica l mean ing o f the minus s ign to the Cor io l i s cons tan t i s tha t the angu la r momentum o fv ib ra t ion , wh ich i s s o r e la ted to tha t o f the ro ta t ion , p roduces an inc reas e angu la r ve loc i ty o fro ta t ion o f the v ib ra t ing molecu la r d ipo le moment abou t the molecu la r ax i s . The p lus s ignmean s tha t the ve loc i ty o f ro ta t ion o f the v ib ra t ing d ipo le mo m en t i s le s s than i t wou ld be i f noa n g u l a r m o m e n t u m o f v i b r a ti o n w e r e p r e s en t . I n t e r m s o f n o r m a l v i b r a ti o n s , t h is m e a n s t h a t


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96 Alkynes and Compounds Containing C~C Groupsthe re i s on ly a s l igh t dec reas e in the ve loc i ty o f ro ta t ion du r ing the as ym. C H 3 s t r e tch ingv ib ra t ion (v 6 ) in thes e m olecu les r e la t ive to wha t the ve loc i ty wou ld be fo r the n onv ib ra t ingmolecu le . A s ign i fi can t inc reas e i s no te d in the ve loc i ty o f ro ta t ion d u r ing the as ym met r ic CH3defo rmat ion (v7 ) , becaus e a l l Cor io l i s coup l ing cons tan t s a r e nega t ive (be tween -0 . 33 and-0 . 39 ) . Thes e r es u l t s a r e wha t i s expec ted i f the CH3 g roup w ere cons ide red to be a s ym met r ica l3 -a rm ed f lywhee l ro ta t ing abo u t a f ixed axi s. The ve loc i ty o f ro ta t ion w ou ld be inc reas ed i f oneor more o f the a rms were ben t toward the f ixed ax i s ; in the cas e o f v 7 the re i s an a l t e rna t ingb e n d i n g o f t w o h y d r o g e n a t o m s w i t h o n e h y d r o g e n a t o m t o w a r d a n d a w a y f r o m t h e m o l e c u l a rax i s . P e rhaps th i s can be more c lea r ly demons t r a ted in Vl0(e) , w h i c h i s e s s en t ia l ly C - X b e n d i nthe cas e o f 1 -ha lop ropyne ; a s h i f t o f s uch a heavy a tom o f f o f the molecu la r ax i s wou ld mos tce r ta in ly s low down the ve loc i ty o f the molecu la r ro ta t ion r e la t ive to tha t o f the f ixed r ig idro ta t ing m olecu le . The o rder o f ma gn i tud e o f the Cor io l i s coup l ing coef f i c ien t s has s ign if i cancein the in te rp re ta t ion o f the IR s pec t r a o f thes e compounds . The l a rge r the va lue the c los e r the Qpeaks a r e s paced in the subban d . Cons equen t ly , a va lue o f appro x ima te ly one m igh t appe ar to benear ly one b road abs o rp t ion band w i th l i t t l e o r no f ine s t ruc tu re due to un res o lved c los e lys paced Q peaks in the s ubband . I t i s s ign i f i can t to no te tha t the pe rpend icu la r ( e ) modes ins o lu t ion o r in the l iqu id phas es appear to be as b road as they a re in the vapor phas e . They d i ff e ron ly in tha t the f ine s t ruc tu re (Q peaks ) a r e no t obs e rved . Th i s s ugges t s tha t in the condens edphases the molecules are s t i l l ro ta t ing, but not as f reely as in the vapor phase (7) .

P H E N Y L A C E T Y L E N E I N V A R I O U S S O L U T I O N SP heny lace ty lene in 0 to 100mol % CHC13/CC14 s o lu t ions has been s tud ied u t i l i z ing F T- IRspectroscopy (14) (see Table 5 .5) . F igure 5 .2 shows a p lot of v=_C-H fo r pheny lace ty lene vsmole % CHC13/CC14 . F igu re 5 . 2 s hows tha t the v=_C-H decreas es in f r equency as the mole %CHC13/CC14 increases . Breaks in the p lot ne ar 10 and 4 5- 55 mol % CHC13/CC14 sugge s t thatdif ferent complexes are being formed as the mole % CHC13/CC14 changes .I n t h e c a se o f p h e n y l a c e t y l e n e i n s o lu t i on , a c o m p l e x s u c h a s 4 ~ - C = C - H - . - C 1 C C 1 3 i ss ugges ted , in in te rmed ia te s o lu t ions o f CHC13/CC14 a complex s uch as

q S - C = C - H . . - C 1 C C 1 3

C13CHand in CHC13 a complex s u ch as

~ b - C = C - H - . - C 1C HC 12

C 1 3 C H H C C 1 3are s ugges ted to exp la in the cha nges in bo th the v = C - H and vC_-__C f r equency changes w i thchange in the s o lven t s ys tem. B u lk d ie lec t r ic e f fec ts o f the s o lven t s a l s o con t r ib u te to the g ro upf requency s h i f t s a s the mole % change f rom 0 -100 .


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Variables in Data Interpretation 97F igure 5 . 3 s hows a p lo t o f vC_=C vs mole % CHC13/CC14 . Th is p lo t s ho ws tha t v C - C

decreases in f requ ency as the mo le % CHC13/CC14 is increased. F igu re 5 .4 show s a p lot of the in-p l a n e - - C - H b e n d i n g m o d e b ip - - C - H v s m o l e % C HC 13 /C C 14 . T h e p l o t s to p s n e a r 6 0 m o l %CHC13/CC14 . The p lo t s tops nea r 60 m ol % CH3/CC14 , becaus e abs o rbance f rom CHC13 mas k st h e a b so r b a n c e o f bip = C - H . T h i s p lo t s h o w s that ~ ip ~C- -H inc reas es in f r equency as themole % CHC13/CC14 is inc reas ed . F igu re 5 . 5 s hows a p lo t o f the ou t -o f -p lane = C - H mo de , ?op= C - H vs mole % CHC13/CC14 fo r pheny lace ty lene , an d i t s how s tha t i t inc reas es in f r equencyas the mole % CHC13/CC14 is increased. The breaks in F igs . 5 .2 and 5 .5 indicate that d if ferentcomplexes a r e fo rming in thes e mole % CHC13/CC14 s egmen ts o f the p lo t s .

Table 5 .5 l is ts IR data for phenylacetylene in 2% wt/vol solut ions in mole % CHC13/CC14s o lu t ions (14 ) . Two IR bands a r e no ted nea r 3 30 0c m -1 in the nea t ph as e an d in s o lu t ion invar ious s o lven t s . F o r example , in hexane s o lu t ion , the s t ronges t band in th i s s e t occu r s a t3322.91 c m - 1 and the s hou lder occur s a t 3311 . 27 c m - 1 whi le in the nea t l iqu id the s t ronges tband in th i s s e t occu r s a t 3291 . 17 c m - 1 and the s hou ld er occu r s a t 3305 . 08 cm -1 . The cha ngesin bo th f r equency and the in tens i ty r a t io o f th i s band s e t i s p roo f tha t thes e two bands a r e inF ermi r es onance (ER. ) , and thes e two bands have been co r r ec ted fo r ER. The co r r ec tedf r equenc ies va ry be tween 3297 . 2 and 3318 . 1 c m - 1 f o r v - - C - H a n d b e t w e e n 3 2 9 9 . 2 a n d3316 . 1 cm -1 fo r the com bina t ion tone . The h ighes t v----C-H f r e q u e n c y e x h i b i t e d b y p h e n y l a -ce ty lene i s when i t i s in s o lu t ion w i th hexane and the lowes t when in the nea t l iqu id phas e .

A p lo t o f 7 o p = C - H c m - 1 v s t ~ i p ~ C - - H c m -1 fo r pheny lace ty lene ( r eco rded in s o lven t s tha twere no t mas ked by the s o lven t s u s ed in th i s s tudy and tha t fo r the nea t l iqu id phas e s how al inea r r e la t ions h ip ) . Th i s ind ica tes tha t bo th modes a r e a f f ec ted equa l ly in a pa r t i cu la r s o lven t ,bu t d i f fe r en t ly in each s o lven t in the nea t l iqu id phas e (14 ) . Thes e da ta do no t co r r e la te we l l w i ththe s o lven t accep to r number (AN) , and th i s may be due to the f ac t tha t the AN va lues do no tr e f l ec t the in te rmolecu la r hydrogen bond ing capab i l i t i e s o f s o lven t s s uch as CH2CI2 andCHC1C13.

1 , 4 - D I P H E N Y L B U T A D I Y N EIn the s o l id s t a te 1 , 4 -d ipheny lbu tad iyne has a monoc l in ic c rys ta l s t ruc tu re w i th two molecu lesin the un i t ce ll . The two mo lecu les in the un i t ce ll have a cen te r o f s ym me t ry (12 ) . The s pacegroup fo r 1 , 4 -d ipheny lbu tad iene i s P 21 /C , wh ich i s i s om orph ous w i th the C2h po in t g roup .Thus , the r ip ( C -C ) 2 , Ag mo de s h ou ld be on ly Raman ac t ive and the V op(C-C)2 , Bu modes hou ld be o n ly IR act ive .

Tab le 5 .6 li st s IR da ta and as s ignme n ts fo r 1 , 4 -d ipheny lbu tad iyne in - -10 % wt / vo lCHC13/CC14 s o lu t ions (13 ) . Raman da ta fo r th i s compound in the s o l id s t a te and in CHC13a n d C C 1 4 s o lu t ions a r e a ls o inc luded . A Raman ba nd a t 2218 .9 ( in C C I 4 ) , a t 2217.8 ( in CHC13) ,and a t 2214 . 4 cm -1 in the s o l id phas e i s a s s igned to r ip (C -C)2 . The IR band a t 2150 cm - t in thesol id s ta te is ass igned to Vop(C-=C)2. The Vip(--C) 2 m ode in the sol id s ta te occu rs 64 .4c m -1higher in f requency than the Vop(C_=C)2 m od e in the sol id s ta te . There is no e vidence forVop(C=C)2 in the Ram an s pe c t rum in e i the r o f the s o lu t ion o r s o l id phas es . The s o l id phas e da taand as s ignmen ts fo r 1 , 4 -d ipheny lbu tad iyne s uppor t the x - r ay da ta (12 ) .

In C C 1 4 s o lu t ion V ip (C=C)2 i s a s s igned a t 22 50 . 5 1cm -1 and in CHC 13 s o lu t ion a t2219 . 45 cm -1 , a dec reas e in f r equency o f 1 . 06c m -1 . In C C 1 4 solu t ion Vop(C=C) 2 is ass ign ed


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98 Alkynes and Compounds Containing C=C Groupsat 2152.23 cm -1 and in CHC13 s o lu t ion a t 215 0 . 22 cm -1 , a dec reas e in f r equency o f 2 . 01 cm -1(see Table 5 .6) . In the IR, the absorbance ra t io [(A)vip(C--C)2]/[(A)Vop(C--C)2] genera l lyincreases as the mo le % CHC13/CC14 increases . As r ip(C --C) 2 is obser ved in the IR w he n 1 ,4-bu tad iy ne i s in s o lu t ion , th i s ind ica tes tha t in s o lu t ion the two ph eny l g ro ups a r e no t cop lanar a sthey are in the sol id phase (13) .

P R O P A R G Y L A L C O H O L V S P R O P A R G Y L F L U O R I D ETab le 5 .7 l is t v ib ra t iona l da ta and as s ig nm en ts fo r p ropargy l a lcoho l , it s -O D and 1 -d and O - Dana logs and p ropargy l f luo r ide (3 - f luo ropropyne) . I t i s he lp fu l to compare the f r equencya s s i g n m e n t s o f a f l uo r o a n a l o g to t h e c o r r e s p o n d i n g O H a n a l o g, b e c au s e t h e C - F a n d C - Omodes occur a t s imi la r f r equency , and the F ana log con ta ins 3 l e s s fundamen ta l v ib ra t ions . TheOH ana log has an add i t iona l 3 fundamen ta l v ib ra t ions . They a re vOH, 6 OH, a n d r O H ( o r O Htor s ion in the vapor phas e ) . The as s ignm en ts fo r the p ropargy l a lcoho l and i t s deu te r iu m ana logsa re inc luded to s how the r eader the va lue o f u s ing the v ib ra t iona l a s s ignm en t fo r co r r e s pon d ingR - F v s R - O H o r R - O a n a lo g s. T h e s a m e w il l b e s h o w n t o b e o f v a l u e i n th e v i b ra t i o na las s ignmen ts fo r Ary l ana logs and phos phorus ana logs .

The in te r es t ing f ea ture in the s tud y o f p ropargy l a lcoho l is tha t in the l iqu id phas e i t does no thave a p lane o f s ym me t ry becaus e CH2 tw is t coup les w i th OH bend ing an d CH2 wag , ind ica t ingtha t thes e funda me n ta l s a ll be long to the s ame s pec ies . Wi th Cs s ymm et ry , CH2 tw is t ing be longsto the a"" sym m etr y species , and c~OH and CH 2 wag belong to the a ' species (15) .

1 , 3 - D I H A L O P R O P Y N E SVapor - and s o lu t ion -phas e in f r a r ed s pec t r a o f 1 , 3 -d ich lo ropropyne a re p res en ted in F igu res 5 . 6and 5 . 7 , r e s pec t ive ly . Comple te v ib ra t iona l a s s ignmen ts have been made fo r bo th 1 , 3 -d ich lo ro -p ropyne and i t s 1 , 3 -Br2 ana log (16 ) . V ib ra t iona l a s s ignmen ts bas ed on bo th IR and Raman da tafo r the 15 fundamen ta l s o f each ana log a re p res en ted in Tab le 5 . 8 . The a ' and a" fundamen ta l sa re due to in -p lane an d ou t -o f -p lane v ib ra t ions , r es pect ive ly . The a ' mode s s ho u ld y ie ld type A /BIR vapor band s and po la r i zed R aman b ands w h i le a" mo des s h ou ld y ie ld type C IR vapor ban dsa n d d e p o l a r i z e d R a m a n b a n d s .

The ba nd a t 2261 cm -1 i s a s s igned to p r imar i ly vC - -C in the case o f 1 , 3 -d ich lo ropropyne . Theband a t 2224 cm -1 i s a s s igned to a co mb ina t ion tone (v~ 4 - V l0) . The two bands a r e in F erm ires onance (ER. ) and thes e two f r equenc ies have no t been co r r ec ted fo r ER. The ER. co r r ec t ionw o u l d l o w e r t h e u n p e r t u r b e d v C = C f r e q u e n c y a n d r a i s e t h e c o m b i n a t i o n t o n e f r e q u e n c y .

A s s i g n m e n t s i n T a bl e 5 .8 a r e s i m p li fi e d b e c a u s e t h e X - C - C = C - X s t r e tc h i n g m o d e s ar eexpec ted to be complex as d i s cus s ed fo r the 1 -ha lop ropynes .

In the cas e o f the 1 , 3 -d iha lop ropynes i t appear s a s though the vC =C mo de i s even morec o m p l e x t h a n i t i s i n t he c a se o f 1 - h a lo a l k yn e . T h e C - C = C - X a t o m s a r e a ll o n t h e m o l e c u l a rax is , and the o the r X a tom i s in the p lane o f mo lecu la r s ymm et ry . There fo re , when the C =Cg r o u p e x p a n d s a n d c o nt r a c ts d u r i n g a c y cl e o f v C = C , t h e C - C o f t h e g r o u p , C - C = , a n d t h e- - C - X g r o u p s m u s t c o m p r e ss a n d ex p a nd . I n a d d i ti o n t he X - C - C - - b o n d a n g le m o s t li ke lydecreas es to a smal l deg ree in the cas e o f 3 -b ro mo prop yne . Co mp ar i s on o f thes e v ib ra t ions fo r1 , 3 - d i b r o m o p r o p y n e a n d 1 - b r o m o p r o p y n e s h o w t h a t t h e se m o d e s o c c u r a t si m i l ar f r e qu e n c ie s .


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Var iab les in Data In terpre ta t ion 9 9v C = C v C - C ~ - v = C - X

Co m p o u n d c m - 1 c m - 1 c m - 11 ,3 -d ib romopropy ne 2226 1064 5121-b romop ropyne 2239 1037 4643-b rom opropyn e 2138 961 3335

T h e v C - C _ = a n d v ~ C - X m o d e s f o r 1 , 3 - d i b r o m o p r o p y n e o c c u r a t h i g h e r f re q u e n c y t h a n th ec o r r e s p o n d i n g m o d e s f o r 1 - b r o m o p r o p y n e . M o r e o v e r , t h e v C = C a n d v C - C = m o d e s a r e h i g h e rthan thos e exh ib i t ed by the 3 -ha lop ropynes . Thes e da ta ind ica te tha t vC~C i s a more complexmo de th an ju s t s t r e tch ing o f the C = C bond . Never the les s , vC--=C i s cons ide red to be a goodgroup f r equency in iden t i fy ing th i s g roup in unknown s amples .

F igu re 5 .8 s hows the expec ted no rm al v ib ra t ions o f 1 -ha lop ropynes , 3 -ha lop ropynes , an d 1 ,3 -d iha lop ropynes (16 ) and the i r f r equency as s ignmen ts . Thes e no rmal modes a r e mos t l ike lyovers implif ied .

P H E N Y L A C E T Y L E N E A N D P H E N Y L A C E T Y L E N E - 1 DTab le 5 . 9 l i s t s v ib ra t iona l da ta fo r pheny lace ty lene and pheny lace ty lene- ld . The in -p lane CC-Hand C C -D bend in g f r equenc ies a r e a s s igned a t 648 and 482 cm -1 , r e spec tive ly . The ou t -o f -p laneC C -H and C C -D bend ing f r equenc ies a r e as s igned a t 612 and 482 cm -1 , r es pect ive ly. Aga in ,the v C -C mo de fo r the H and D ana logs occur a t 2119 and 1989 cm -1 , r e spec tive ly , and th i s isa t t r i b u t e d t o c o u p l i n g b e t w e e n v C = C a n d v C - D ( 1 7 ) .

As s ignmen t o f the r ing modes w i l l be d i s cus s ed l a te r .

R E F E R E N C E S1. Ny quis t , R. A. and Pot ts , W. J . (1960) . Spectrochim. Acta, 16, 419.2 . Evans, J . C. and N yquis t , R. A. (1963) . Spectrochim. Acta, 19, 1153.3 . Nyquis t , R. A. (1985) . App l. Spectrosc., 39, 1088.4 . Nyqu is t , R. A., Reder, T. L., Ward, G. R., and K al los , G. J . (1971 ) . Spectrochim. Acta, 27A, 541.5. Ny quis t, R. A., Reder, T. L., Stec, E E, and Kallos, G . J. (1 971) . Spectrochim. Acta, 27A, 897.6 . Evans, J . C. and N yquis t , R. A. (1960) . Spectrochim. Acta, 16, 918.7 . Nyquis t , R. A. (1965) . Spectrochim. Acta, 7, 1245.8 . Davidson, D. W., Sundaram, S., and Cleveland, E E (1962) . J . Chem . Phys . , 37, 1087.9 . B oyd, D. R. J . and Th om pson , H. W. (1952) . Trans. Farada y Soc. , 48 , 493 .

10. Gr i sen thwa i t e , H. A. J . and Th omp son , H. W. (1954) . Trans. Farada y Soc. , 50, 212.11. Lord, R. C. and Merrifield, R. E. (1952). J . Chem . Phys . , 20, 1348.12. Wiebenga, E. H. (1940) . Z. Kristallogr., 102, 93.13. Nyquis t , R. A. and Putzig , C. L. (1992) . Vib. Spectrosc., 4, 35.14. Nyquis t , R. A. and Fiedler , S . (1994) . Vib. Spectrosc., 7, 149.15. Nyquis t , R. A. (1971) . Spectrochim. Acta, 27A, 2513.16. Nyqu is t , R. A., Joh nson , A. L., and Lo, Y.-S. (1965) . Spectrochim. Acta, 21, 77.17. E vans, J . C. and N yquis t , R. A. (1960) . Spectrochim. Acta, 16, 918.


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Alkynes and Compounds Containing C≡C Groups

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Transcript of Alkynes and Compounds Containing C≡C Groups