472
MARTIS H. LITTLE .4ND ARTHUR E . MARTELL
16. The regreening of oranges in Florida is an effect of environment. 1’7. The flowers of Sweet William come nearly white vhen not exposed t o ultraviolet light. 18. The number of four-leafed clovers in a patch varies with changing environment, increasing in hot n-eather. REE’EKESC .kLL4RD: J. Agr. Rese:tVch 57, 10 (103Si. ALTARI)A X U G A R W R :J. .igr. Research 63, 305 (1941 1 BAXROFT:J . Phj-s. Colloid Chem. 51, 1083 (19471. RRIUGE:1Ll:yrian S p r i n g , 1). 135. Little, I3rowri :iricl (:omp:tri>-, Boston, AIassnchusetts (19351. ( 5 ) FLETCHER: Proc. .1111. FIo1,t. Soc. 26, 191 (1029). (6) GARSER:Rotari. l l c v . 3. 268 (1937), (T) GARSERASD ALIARU: 1-carbook of the I:. S . Department of‘ Agricidhre, Washington, D. C. (1920). (8) GARNERA N D ALLARI):,J. .ig. Research 31, 555 (1925). (9) HEIN:Bull. mens. S O C . linneenne Paris 2, 932 (18911. (IO) HILLES: Vermont Agr. Espt. Sta. Bull. S o . 103 (1903). ( l l j HOLDSWORTII .&si) SCTXIAS: S a t u r e 160, 223 (1947). (12) H o u s ~ Wild : Florcem, p . 205. The 1I:~cmill:~n Company, S e n York (1935). (13) Reference 13, p . 220. (14) hIcC.4~:Am. ,J. Pub. I I e d t l i 37, 321 (1947). (15) ~ A T T O : u r FlorwritLg It’orld. Dodd, Meat1 anti Company, S e n Tork (1947). (16) Reference 15, p. 179. 117) PIATT: This Green Il.or./ri. Dodd, AIcntl xntl C‘ompnny, S e w I-ork (19421. (1) (2) (3) (4)
IZ .UIAS SPFYTK.~( )F 11w Depaitiiit
nt
rts (li
11 IxrmE,?
(‘hc
ittiall
y.
ClrriX
.mrr.iw
\HTHPR I; MARTELL f * n i i t rsitu, I170rcester,
Massachiisefts
Iieccii cd J i i l i l 17 1948
Since acetals contain t u o ether lmhages utt:tched t o the yame carbon atom, it \vas decided that it < t i d y of the Etaman spcctra of a series of acetals would be of interest. Hibbcn’i hihliography ((i),\\ hich coveis Raman literature up to 1939, and a search of thc literature iincc 1939 iwealed that no paper has been puhliyhed cwncerning the Itaman spectia of thew c*ompoiinds. hlthough it a- clrritlctl t o prrparc -wcixl homologoiis ~ r i e sof acetals, it was found that somc of thc wrtal- (wild not tw prepared ti\- the usual method, as described by X d k i n ~and Sisben (4). ‘I’hc preparation of these acetals by anothci. method ha\ h e m po-tponecl t o ii late1 clnte I t \ \ a + also found that 1 lbstractcd from ‘L dissertation prcsentetl lj\ AlaitLri I€ 1.ittlc t o the E‘iculty of Cltlrb I-nivcrsity in pnrtial iulfiilnic~ritoi the rcquiic~nicntsfor t h o tlcgrcr of Iloctor o f I’h1losoph.r , h u g u s t , 1946 I’rewnt addrebs I>ep,ii tnient of (’hemisti\ I ~ i r o i i( olieyc, Schenectatiy. S e w Tor6
RAMAX SPECTRA OF ACETALS
473
Raman spectra of sufficient strength could not be obtained from some of the acetals prepared. *in attempt has been made to assign the frequencies observed to the vibration of the molecule that garve rise to them. mathematical treatment to correlate frequencies and vibrations was not attempted, since acetals have only one degree of symmetry. The molecule of diethyl acetal, the simplest substancc investigated, ha> 22 atoms and, according to Herzberg ( S ) , such it structure require. a secular equation of 66 columns and 66 rows. Because acetals have only one degree of symmetry. the secular equation cannot be reduced to an easily d v e d problem. IPP I R 1 T r h
Liylr t so 11 rce The light source \vas :I Hanovia helical quartz mercury arc operated by :L 6000-v. A . C . current The reflector \\-as a chromium-plated sheet-iron cylinder. Thi- cylinder \vas made in t\vo sections so as to fit around the helis lamp.
Raman tribe 'Flit. quartz Raman tube had a diameter of 2 cm. and a capacity of 25 ml.
It \vah equipped n-ith a jacket (also made of fused quartz) which served as x cooling jacket and also as a filter jacket. The annular space between the Raman tubc and jacket was 1.2 em. The jacket and Raman tube were assembled Jvith numher 104 black rubber gasket.. The length of Raman tube exposed to exciting radiation was 7.5 em. The light emitted from the planar bottom of the Raman tube u-as reflected into the spectrograph by a chromium mirror, which ~ v a bcut from highly polished chromium-plated sheet metal and was set into the base of the holder at a 4.5"angle. This holder was made so that the as5embled Raman tube slipped into a collar and was centered over the mirror. T h r light from the mirror as reflected through a carefully centered 6-mm. hole 111 :I diaphragm attached to the holder. By means of this diaphragm the holtlw \ \ a - slipped onto the Hnrtmann diaphragm track in front of the slit. ?'e mpe ra t ii re control
The. cooling \\ ater \ \ a s circulated through the jacket by means of :t centrifugal pump, and \I as maintained at a constant temperaturr by circulation through a glass coil immersed in a constant-temperature bath. The tc>mperatureof the bath varied by i O . l " C . , hut there \ \ a b no observable change in the temperature of the circulating tem. -1thermometer included in the ciicuit by means of a T-tube recorded the temperature of the filter soliition as it left the bath and entered the cooling jacket. ail 1)ubt)les in the system \rere eliminated b y an air trap which \va* simply an opening in the bystem rsposing a relatively large surface of the liquid. This trap \vas placed ithove the centrifugal pump on the inlet side. -1g l n b - \\-ool filter \\-as included In the circuit to remo1.c solid particles.
474
JIARTIX H. LITTLE . ~ S D ARTHCI!
E. ; \ I . m r E L L
Spect royraph -4 Hilger medium quartz spectrograph \\-as used. The slit xidth used 1~:s 50 (0.05 mm.). This instrument has a dispersion of 55.5 -!.,.’mm. a t X 4500 -4. Most of the work in the literature has been done ~ i t the h mercury exciting line A 4358 -1.(hereafter referred to as Hg 4358), but it is seen that with the spectrograph available the dispersion in this region is not very high. A41so,when using Hg 4358 it is necessary i o use a filter so that Hg 404T Trill not give overlapping Raman spectra. Through the use of a quartz mercury arc and quartz Raman tube it was 110ssible to employ H g 2537 as the exciting radiation. The region from 2537 -k. to approximately 3000 -1.shows practically n,o liackground and in this region the dispersion of the I-Iilger spectrograph is 11 ;1. mni.
Microphotometer Intensities of the Raman lines u-ere measured liy :i Leeds cL. S o r t h r u p recording microphotometer. Tracings \\-ere made at 21 plate speed of 3 mm. per minute. The longest d i t of t h e microphotometer \vti. used.
I’laies
Eastmnn spectroscopy plateh t\-pcx 103-0, ulti.a\.iulet sensitized, \\.ere used. De;.elopment I Y ~ .5 S min. a t 18°C’. in I prepared, di-n-amyl acetal, dimethyl i n t y r d , and diethyl hutyrnl, h a r e not previously been reported. -Also, the iensitie- and indices of iefraction have not previously been reported for a11 he acetals listed, with the exception of diethyl acetal. Dimethyl propional b.p. 121-122"C.), diethyl propional (11 p. 123"C.), diisopropyl propional (13.p. 11°C'. a t 05 mm.), diiwbutyl propional (b.p. 127-128°C. at 88 mm.), and liisopropyl lmtyral (11.11. I(jI"C'.) were alqo prepared but were not investigated urther. since their Raninn ipectrn v.eie too weak t o allon- satisfactory measirement . TABLE 1 Ph vsical constants of acetals prepared BOILISG P O I Y I
LITER i T U R E
ACETAL
REFLRLSCE
~
~~
Literature .
'C.
Xetliyl acetal. . . . . . . . . . . . . . . . . . )i-n-propyl ncetsl, . . . . . . . . . . . . . . . . . . ) i -TI -but y1 w e t a1 . . . . . . . . . . . . . . )i-n-amyI acetal . . . . . . . . . . . . . . . . )iisoamyl a c e t a l . . . . . . . . . . . . . . . . . . . . . )imethyl h u t y r a l . . . . . . . . . . . . . . . . . liethy1 b u t y r a l . , . . . . . . . . . . . . . . . . . . . ~~
~-
(11) (11) (11)
_ ~ _ _ _ _ _ ~ ~ ~ ~
104 147 198-200
(11)
211 1
___
Found
______
"C. 104 144-116 190 220-222 200 112 146
REFR\CTIIE
Iwrs 25 "D
__
1.3948 1.4073 1.4152 1.4090 1.3882 1.3946 ~. -
E X I ' E R I J I E S T I L RESGLTS
The wave numbers of Raman lines measured for the acetals listed in table 1 :e given in table 2, together with the relative intensities. The spectra were 2terminetl a t 20°C. for 12 lw., those of diethyl acetal and diethyl butyral being le IVeakeST. Increasing the exposure time in these tn-o cases seemed t80have ttle effect. I n the case of the acetals n-hich gave no spectra, it is beliered that, small amount of unrenLted ddehycle may have been present, since all alde)rh in the 2 5 3 i .i. region. The intensities listed are based on tracings atle on u Leeds cb Sorthrup recording densitometer. I , \\-as determined by ultiplying by 10 the rntio of the height of the line to the height of 0 to 100 per ,nt transmission scale. 11Ieasurements of heights \\-ere macle above bacli,ountl adjacent to each Kaman line, i.e., the hacligro~intladjncent to each :imaa line represented zero tranumihsion. .iSSIGSJIEST O€ FREQTESCIES
$inw a mathematiccll trwtment \vas not feasible, assignment of frequencies .s been made by comparison n i t h the c1i:micteristic frequencies of alcohols,
476
JIARTIS H. LITTLE AKD ARTHUR E . MARTELL
aldehydes, and ethers. I n table 3 the Raman frequencies of diethyl acetal are given together \\-ith the tentnt ivc absigninent of the vibration which ga\ e ri?e T 113L1, 2 Il’aLe
~-
~-
L
in
~ ___ fin
1
341 524 803 851 916 1036 1103 1156 1276 1450 2654 2732 2803 2882 2938 2986
1
’
’
-
7 5 S 0 b 0 6 5 6 5 6 5 6 0 80 4 5 6 0 5 0 90 8 5 6 5 7 0 8 0 8 0 7 5 S 5 7 0 7 0 9 5 8 5 6 0 6 0 80 8 5 9 0 00 10 0 10 0 10 0
,
\\ a\ e number
_ _ __
~
Cllt
1
15 241 10 299 10 330 388 10 0 5 417 1 0 432 1 4 483 1 0 9 535 1.0 654 2 5 i57 1 2 0 1 847 3 0 1 884 3 5 I 906 7 0 966 80 997 I 7 5 1065 I 1139 1 1176 1252 1290 1343 1 1458 I 1488 I I 16i1 1678 2597 2676 2731 2794 2874 2938 2078
-
~~
11 a \ e number
\\ a \ e number
~-_
012
241
b 5
290
5 6 5 60 65 7 5 3 5 1 0 7 0
373 424 476 542 661 733 810 839 902 920 1026 1072 11-17 I160 1230 1259 1311 1351 1388 1449 14% 1545 1666 2204 2271 259i 2659 2738 2704 2858 2898 2916 299-1
5
1
0 0 b 0
I
80 5 0 b 3 5 0 7 0 7 5 0 0 7 5 i 5 0 5 7 5 45 1 3 0 15 15 7 5 X 5 9 0 9 0 10 0 10 0 9 5 0 5
Clll
1
261 15 2 0 ,395 542 2 0 2 5 780 55 ’47 877 50 3 0 006 3 5 981 5.0 1065 50 1132 1306 6 5 3 0 1343 3 5 1381 S 0 1412 1678 1 5 0 2668 1 4 5 6 5 2747 2786 1 6 5 2883 10 0 2914 1 10 0 2938 10 0 2970 I1 0 2994 8 5
1
__
-
~~
__
~
~
D1 T H \ L BIT\K\L
DIUETHlL HLT’IKAL ~
I
~~-___
11 a i e numbei
\I a\ e number
__
0 0 5 A 5 6 5 60 6 5 3 5 8 0 80 h 5 7 0 S 0
322 336 417 461 520 550 639 712 832 S7T
921 ‘I70 1033 8 0 1065 7 5 1140 7 U 1199 7 0 1244 7 5 1275 0 0 1306 8 5 1365 7 0 1457 7 0 1541 8 5 2590 5 5 2684 0 5 2738 7 0 2S3-i 3 5 28i4 7 0 2930 S 0 2094 0 0
‘
< )I. -
CIII - 1
1
264 307 388 124 446 491 550 661 768 783 832 884 914 960 980 1011 1033 1065 1147 1176 1225 1268 1306 1343 I458 1488 1541 2634 2651 2773 27i9 2883 2906 2938 2962 2m-1
_ _ _
~-
DIISO i U \ L \CFT \L
-
\f a\ e number
o l cicclnl\ O h f e d or f u b i c 1 ~
III 11 iii TIL \ TT\L
DI-II-PROP\L kCET4L
\\ a \ e
~
~_____
- ~-
4CLT1L
number
ititrtirc rtitcnsitits
t r t i i i i b e ) ~u i i d
7 5 8 0 6 5 4.5 4.5 5 0 5 0 3 0 6 5 6 0 7 5 7 0 I 7 5 7 5 7 5 40 3 5 4 5 6 5 6 5 1 9.0 4 5
322 824 913 1049 1101 1154 1275 1448 2651 2731 2803 2S74 2938 2978
1 5 10 1 0 1 0 15 1.0 10 3 5 1.0 2 0 2 5 7 5 5 0 7 0
’
i.O
8 0 8 5 9 5 10 0 10 0 9 5
1
0 0
10 0 10 0 10 0 10 0 0 5 ~-
to them. The value? in parent1~e.e~a 1 e the (*oii~~.pondingdimethyl ethm frequencies ( 3 ) . &I11Iiaman frequencies mentioned in the iollon ing dimi-w)ri are giren in \lave numhei-. Diethyl ether has no fiequenries in the 800 legion. ‘Yhebe t n o frequencw.
undoubtedly are clue to C-C' vibration. Herxherg lists the C--C bond stret,ching as 900. In ethane the value is as high as 993 but decreases as the molecule becomes more complex. This is pointed out by Hibben ( 6 ) - and he gives t'he range of 800 t o 1100 a s the frequency range for C--c' valence vihration (stretching). The aiithors \ ~ o u l dassign the lower value, 803, to the ('-(' vibration in the aldphytle side and the higher value, 831, to the vihration of the cwhons in the alcohol part of the acetal. ;Ilthough the w i g h t attached t o each of the inner carbons is practically the same, the tn-o osygens attached t o these inner ctrbons should havc a direct effect on the C'-C vibrations The inner carbon of the aldehyde chain has tn-o osygens on it, \\,bile the inner c:irhon of the alrohol chains lins only one nnd hence should ha1-e the higher flwiiiency. I t is t o IN: TABLE 3 Ramari jreqitericies o j d i e t h y l ucetal. ~
~
~~~~~
FREQLTSTY
VIBR
~~~~~
~~
~
__
~
jnrms
~~~~~~~~~~~~~~~
~
~
cm-1
0 10 . . . 1 1 . . . 12 . . 13 . . . . . . 14 . . . . .
311 521 603 S5l 916 1103 1155 12i6 1450 2651 2732 3803 2882 2938
15..
2986
1 2 . . . 3 . . . .
4 . .. .
.
5 . 6 . . . .. 1
s
~~
. . . .
. .
, . . .
CH3 twist,ing? (300?)" CH, twisting? (583?) C-0 swetching (91s) C-0 stretching (11001 CH, rocking (115.5) 6 + 7 ? CH: deformation (l1fS1 7 + 9 ? 3 X 5 ? C-H symmetric stretcliiiig (2802) 2 X 9 ? C-H hot h synimet ric ;rnd noli -synimet ri c stretching (2916) C-H non-symmetric st retching (2986j ~
~
~~
~~~~
~~~
..~
* V:rlues in parentheses are the corresponding frequencies for clinirthyl ether.
noted that the intensity of the 851 line is greater than that of'the 803 line. This should be expected, since there are two oscillators giving rise t o the 851 line and only one oscillator for the weaker line. The assignments that Herxberg gives t o the frequencies 300 and 583 of dimethyl ether are not certain. In the spectrum of acetal the two lowest frequencies are not very close to either of these values. Hihben (6) a t t r i h t e s those frequencies helo\\- 600 a$ heing due tjo C--C transverse vibrations. He gives no reason for this statement but his assignment is in keeping with Mecbe's proposal ( i ,8, 9). Dimethyl et'her possesses C-0--c' bending vibrations and since the C--0--C group is similar. t o the C--C-C group, i t is possible that one of these frequencies is a bond-bending frequency. For propane Herzherg ( 5 ) list's the vibration 3 i 3 as C-C-C bond bending. Indirectly, he arrives a t a value of 333 for CHa twisting and he gives no value for C'H, twisting.
478
M i R T I S H. LITTLE .1SD .iRTHUR E . X i R T E L L
S o t enough information is available a t the present time to positively assign all lines in the 200-300 region. Because C H twisting and C--0-C and C--C’C frequencies which occur in the range 200-600 are “outer” vibrations, no dehnite assignments can be made from mere comparison of compounds. Only the general statement can be made that these frequencies lie in this region. There is one vibration in the 523-350 region which seems to be satisfactorily constant from compound to compound and is to be designated as an “inner” frequency. With the exception of diethyl ether and butyl alcohol, neither alcohols nor ethers h a w frequencies in or near the 525-550 region. The hydrocarbons shou- no conaiqtent frequency in the 300400 region, and lower members have no frequencie- nt all in thi.: range. Perhaps the 312 line arise5 from 400
200
600
IO00
300
1400
I200
2600
1600
2800
2000
PYL YL
L
I 1
I
I
I
I l l I l l
I
I
I
rl
200
400
600
300
1000
1200
1400
1600
2600
2800
3000
FIG.I . Rnmnn spccti:i of :icct:ils
C-C=0
bending, \\bile in ac.etnls the 5-10 line may tie nssociated with the
-0-C-0-
group, n-hich is common to d l acetals but is not found in ethers
H or alcohols. The aldehydes have a very wnstant frequency at 512. The ahPence of a line in the 340 region for diethyl ac*etalmay h e due t o it> \veal; spect rum. The 1103 frequency in diethyl acetal I\ hich, from comparison ith diethyl ether, has been assigned tentatively the C--0 stretching vibration is not found in any of the other acetals except diethyl butyral. -In examination of figure 1 or table 2 indicates that the 1103 frequency decreases to 106.5 in di-n-propyl acetal and then remains constant through the rest of the acetals, but there is no evidence that this should be so. If this C--0 vibration is an "enter" vibration, a decrease in vibration from compound t o compound would lie espected and such a decrease can be follon-ed in the frequencies 1103, 106.5, 1026, 981, 960. Except for the last two values a rather constant difference of -10 is found between successive lines. However, there is not enough information obtainable a t preaent to positively assign frequencies in this region to the C-0 vibration to Tvhich Herzberg has assigned the 1100 frequency in dimethyl ether. -1s indicated by Hibben (6) the region 600-1100 contains C-C stretching vibrations. Since
most of them are not **inner"vibrations, there is difficulty in assigning ,given lines t o given vibrations. Since the C-0 bond is similar tu the C-C bond, its vibration will be found in this region along 11-iththe C-C: vibration. The frequency 1160 in diethyl ether has been assigned by Herzberg (5) t o CH, rocking. In diethyl acetal a frequency is found a t 1160 ant1 is found to ] ) e quite constant for all acetals. Similarly the frequency 916. xhich arises from ivliat Herzberg calls C-0 liond stretching, is quite constant from acetal to a c et a1. I n di-)i-amyl, di-ti-butyl, and diisoampl acetals there seems to be a splitting of the 1156 lines. Since the spectrum of tli-u-amyl acetal was n-eaker than the others, perhaps the line or lines which should have appeared in this region did not photograph. Collins (2), in his study of alcohols, remarlis &at the lines in the 1000-1200 region exist in pairs independent of chain and only slightly :iEected by the end radical. V o o d and Collins (13) in n lat'er paper call 1055 and 1075 a double line and attribute these frequencies t o ,sidewise compression of the carbon chain. S o such pairs of lines seem to exist in the spectra of acetals. By analogy, it is possible that, splitting of the 1156 line is caused by siden-ise compression of C-C-C interacting n-ith the C-0-C vibration. The line at 12iG in diethyl acetal has been proposed in table 3 as a possible combination line, but, Trumpy (12) assigns vibrations in the 1280 region to the grouping CI-13-C€12- and calls it an "inner" vibration \\-hich varies only i10 from alcohol to alcohol. This line is riot found in :ilcohol.~xhich do not h a ~ e tlie CH3-CHgroup (see Hibben (6) and n'oods antl Collins (13)). Collins ( 2 ) mentioned the 1300 line and attributed it t o an cncl C",:vibrating :Lgnin.t the rest of the molecule, brit K o o t l and Collins (13) remai,li that this is unlikely, since the frequency is relatively constant and does not diminish with lcngth of chain. This is the only comment they niake concerning this line. The ncitls anti hytirocarkmis seem t o have a line in the 12i5-1300 region :ind some assuciation ivith thc CR,:--C"s group can be follon-etl. -\ippai,entlj- tlie 12'76 frequency foiind in acetal antl other compounds is not strictly ; i n ' ' inner" frequenvj-, since there seenib to lie in the case of the higher acetals :in wy-mnietric splitting :ind \viclc variation from the original value of 12iG. 'I'he ('€Is tleformation frequency 1450 (see Datlieii ~ r n c lT:inbe posit ivcly identified in a compound containing the CHs group. -4lso outstanding is the frequency 1488 Ti-liich appear> in cli-rt-propyl acetal. 'This frequency has the same T-alue in all the higher acetals. Of the alcohol5 only ethyl alcohol has a line in both 1430 and 1485 regions, u-hile butyl alcohol has a line at' 147G 11ut no line at' 1430. The aldehydes have nu lines in the 148.5 region, but all the ethers (except dimethyl) up t o dibutyl (see Cleveland (1 1 ) (lo have a line in this region. Thus this line seems t o 1.w associated ivitli the ether linkage and a t least tn-o carbons on one side of thc oxygen (since this frequency is found in the dimethyl butyral spectrum m t l not in the dinit thy1 ether .qiectrum).
4x0
JIARTIS H. LITTLE 1 S D ARTHUR E. MARTELL
Not present in diethyl acetal nor in di-n-propyl acetal hut appearing in di-n-
butyl, diisoamyl, and dimethyl butyrals is the line 1.541. (The absence of this line ip diethyl acetal, di-n-amyl acetal, and diethyl hutyral may be due to the fact that their ipectra are neaker.) The 1.541 frequency seems to he peculiar to the acetals, in that no frequencies occur in this region for alcohols, aldehydes, or ethers. Hibben (6) malies the general statement in hi5 (lisciwion of hydrocarhon.; that the frequencie4 :hove 1100 (but leba than 2600) are usually attributed t o C-H deformation (tramverse or bond bending). The hydrocarbons, hoivever, have no frequencies :hove 1500 and only t n o have frequencies near 1483. Thus it cannot he certain that the acetal frequencies 1488 anti 1341 a l e C’--€’L deformation frequencies. From comparison with Herzberg’s adgnnient t o dimethyl ether, linc 2803 in the acetal spectrum has heen assigned C-H symmetrical stretching vihration and the 2882 line hah been considered an overtone. The 2803 line is u ealier than 2882 and fundamental vibrations are usually stronger than combination or overtone vibrations. It \roultl seem, therefore, that 2882 is a valence vibration and not an overtone. Trumpy (12) does assign a fundamental C-H vibration frequency appearing in the 2870 region. He assigns this frequency and another frequency, 2923, (in xlcohol) to hydrogen lwnd stretching vibrations in the grouping : I€
H
In the acetals strong lines lie in the 2880 and 2933 regions. These lines remain rather constant from compound to compound, although there seems to be n slight shift toward higher frequencies. Lllso,there seems t o lie splitting of the 2880 line in di-n-hntyl, di-n-amjrl, and diisoamyl acetals. In the case of the alcohols tthe number of lines in the 2800-2900 region reaches three, and as the straight-chain alcohols get longer the number reduces to tn-o. Trumpy makes 110 comment on t,his, other than to point out the extra lines or the absenc.e of certain lines and g r ~ u p sthem all together under C-H vihrations of the H
H-C-C I
H group. The vibration 2 0 6 i in :tlcoltol~ i, iittrihutecl to (‘ -H vibrations in either of t\vo grouph: H H
\\-here I' i q u h i d l y carhon. In the acetals this vibration apparently has the 2944 frequency ivhich appears in the Raman spectra as a very strong line. Herzherg calls thic vihration a C-€I non-symmetric vibration. This frequency remnin4 \-cry conqtant throughout the compounds studied. ('os('I,T-sIos
I he linm ai.ising from C - 4 ) rtretching jn the 924 i~.gioii.C-0-V rocliing in the 1150 region, CH, bond bending in the 1450 region, and C-H honcl stretching in the 2880, 2935, antl 2994 regions can he clcfinitcly assigned in the acetals. Since t'hese lines arise from '. inner" vibrations and are quite constant, from compound to compound they can be readily identifiiccl. Other frequencies in the 320, 1488, and 1541 regions have been found tu lie rather constant from cwmpouncl to compound and therefore are suspect,ed of group has heen heing inner" frequencics. The vihration of the O-C'-O suggested as the cause of the frequency in the 320 region. The 1488 frequency seems to he associated with the ether linkage, while t h e 1,541 line seems t,o hc characteristic of acetals alone. Other vibrations ii-hich are "outer" T-ibrations and vary from compound to cornpound cannot be definitely assigned. Because other frequencies appear in the same regions, one given frequency which r-aries from (,ompound t o compound cannot be positively follon-ed. 7
-
hY111iARY
The Kaman spectra of diethyl acetal, di-n-propyl acetal, tli-ri-butyl acetal, di-??-amylacetal, diisoamyl acetal, dimethyl butyral, antl diethyl butyral have been determined for the liquid state and the relative intensitjes of the lines have been measured. -4comparison of the frequencies with thobe of alcohols, aldehydes, and ethers has been made, and a tentative asrsignment of frequencies has been attempted for somc of the Raman lines. Tables of frequencies are given. The aut,hors express their appreciation to the Physics Department of Clark I-niversity for granting use of the spectroscopy laborat,ory and equipment, to the American Steel and Wire Company of Worcester, Massachusetts, for the use of its Leeds & Sorthrup densitometer, and to Richard Brown of Clark Vniversity for assistance in preparation and determination of the physical constants of the acetals. The authors are also indebted to Dr. Roy C. Gunter, Jr., (if Clark Vniversit8yfor many useful suggestions in the manipulation of the nppara-
tus. It E: FI.:RE s c E X F. F..~ I V R R . I Y H.> J . ,
N A S E Y , H. I I . . .\SI)s € i . 4 ( ' K E L F O R U , J. : J. ('II(Y~I. Phys. 8, 1.53 (1940). (2) COLLISS,G . : Phys. RPT. 40, 820 (1932). ( 3 ) D . 4 D I E C , .-i.: .\SI)KOHLRACSCH, I
