C5H8   -   Isoprene

Molecular constants for trans-isoprene (2-methyl-1,3-butadiene)
Parameter t-CH2C(CH3)CHCH2 Ref.
Rotational Constants
A″ [MHz] 8527.025(7) a
B″ [MHz] 4175.529(17)
C″ [MHz] 2852.170(6)
τ1 [kHz] -29.4(3)
τ2 [kHz] -6.64(96)
τ3 [kHz] 100.7(102)
τbbbb [kHz] -4.97(82)
Derived Constants
DJ [kHz] 6.22(52) a
DJK [kHz] 5.49(53)
δJ [kHz] 0.31(5)
Internal Rotational Constants
Iα (u Å2) 3.132 (assumed) 69058
θ 6.173 (assumed)
V3 (cm-1) 917.(35)
Electric Dipole Moment
µa [C · m]
    µa [D]		 0.117(7) x 10-30
    0.035(2)		 64028
µb [C · m]
    µb [D]		 0.834(33) x 10-30
    0.25(1)
Magnetic Constants
gaa -0.0621(13) µN 70065
gbb -0.0339(16) µN
gcc 0.0080(16) µN
2χaa - χbb - χcc 16.7(12) x 10-6 erg/(G2 · mol)
-χaa + 2χbb - χcc 19.2(10) x 10-6 erg/(G2 · mol)
Qaa 1.7(2.2) x 10-26 esu · cm2
Qbb 3.3(2.3) x 10-26 esu · cm2
Qcc -5.0(3.2) x 10-26 esu · cm2
 
a J. Phys. Chem. Ref. Data 18(3), 1245-1524 (1989).

 

 

C5H8   -   3-methyl-1-butyne

Molecular constants for 3-methyl-1-butyne (isopropyl acetylene)
Parameter HC≡CCH(CH3)2 Ref. Parameter HC≡CCH(CH3)2 Ref.
A″ [MHz] 7969.491 23(2168) a A [MHz] 7969.48(2) 73079
B″ [MHz] 3828.800 99(293) B [MHz] 3828.801(2)
C″ [MHz] 2833.239 99(258) C [MHz] 2833.216(2)
τ1 [kHz] -50.1343(107 27) DJ [MHz] -2.29(17) x 10-3
τ2 [kHz] -10.6737(3265) DJK [MHz] -71.0(35) x 10-3
τ3 b [kHz] 202.82(8) DK [MHz] -0.1128(38)
τaaaa [kHz] -22.248(3856) Dwj [MHz] 0.89(4) x 10-6
τbbbb [kHz] -4.433 47(230 10) Dwk [MHz] 23.2(10) x 10-6
τcccc [kHz] -0.839 60(28 223)  
Electric Dipole Moment
  µa [C · m]
    µa [D]		 2.282(27) x 10-30
    0.684(8)		 73079
µc [C · m]
    µc [D]		 0.757(13) x 10-30
    0.227(4)
 
a J. Phys. Chem. Ref. Data 18(3), 1245-1524 (1989). Note units for the distortion constants should be kHz as shown here.
 
b The value of τ3 is fixed by setting R6 = 0.

 

 

Rotational constants for the excited vibrational states and isotopic species of 3-methyl-1-butyne (isopropyl acetylene)
Species A [MHz] B [MHz] C [MHz] Ref.
(CH3)2CHCCH     ν19 8035.7(5) 3833.19(2) 2837.93(2) 73079
(CH3)2CHCCH     ν23 7963.4(11) 3825.45(4) 2830.30(3)
(CH3)2CHCCH     ν24 7916.7(4) 3840.43(2) 2832.66(2)
(CH3)2CHCCD 7957.2(5) 3553.60(1) 2681.19(1)
13CH3(CH3)CHCCH 7776.4(12) 3791.51(4) 2788.91(4)
13CH3(CH3)CHCCD 7763.0(7) 3519.01(2) 2640.07(2)

 

 

C5H8   -   1-Pentyne

Molecular constants for the ground vibrational state of trans- and gauche-1-pentyne
Parameter trans-1-pentyne gauche-1-pentyne Ref.
A″ [MHz] 23 382.(66) 9921.116(21) a
B″ [MHz] 2230.560(15) 3172.7689(36)
C″ [MHz] 2116.362(15) 2634.0128(36)
τ1 [MHz] 0.0423(75) 0.033 55(90)
τ2 [MHz] 0.002 47(53) 0.002 203(202)
τ3 b [MHz] 0.6(6) 0.472(6)
τaaaa [MHz]   -0.1777(116)
τbbbb [MHz] -0.001 66(70) -0.018 440(115)
τcccc [MHz] -0.001 49(65) -0.004 336(140)
Centrifugal Distortion Constants
DJ [MHz] 0.000 38(4) 0.0022(3) 71046
DJK [MHz] -0.013(1) -0.016(2)
DK [MHz]   0.45(5)
Electric Dipole Moment
µa [C · m]
    µa [D]		 2.797(2) x 10-30
    0.8385(5)		 2.292(7) x 10-30
    0.687(2)		 71046
µb [C · m]
    µb [D]		 0.527(23) x 10-30
    0.158(7)		 1.057(13) x 10-30
    0.317(4)
µc [C · m]
    µc [D]		   0.23(7) x 10-30
    0.07(2)
 
a J. Phys. Chem. Ref. Data 18(3), 1245-1524 (1989).
 
b The value of τ3 is fixed by setting R6 = 0.

 

 

Molecular constants for excited vibrational states of trans- and gauche-1-pentyne
Species Vibrational
State a		 A [MHz] B [MHz] C [MHz] E (cm-1) Ref.
trans-1-pentyne ν33=1 (22 200) 2231.75 2121.08 106(10) 72063
ν33=2 (2 1500) 2233.09 2125.94 213(25)
ν33=3 (20 500) 2234.66 2130.97 330(30)
ν33=4 (19 500) 2236.32 2136.16 426(30)
ν32=1 (23 800) 2235.63 2118.28 166(15)
ν32=2 (23 900) 2240.58 2120.13  
ν33=1, ν32=1 (22 700) 2236.33 2123.07  
ν31=1 (23 000) 2228.39 2114.99 253(20)
ν33=1, ν31=1 (20 400) 2229.88 2119.39  
gauche-1-pentyne ν33=1 9974.64 3165.12 2629.18 114(10)
ν33=2 10 032.33 3156.99 2624.26 223(25)
ν33=3 10 092.15 3148.34 2619.26 323(30)
ν33=4 (10 163) 3138.43 2613.71 425(30)
ν32=1 9948.04 3175.51 2634.81 177(15)
ν32=2 (9968) 3178.12 2635.47  
ν33=1, ν32=1 10 000.17 3167.50 2629.93  
ν31=1 9881.04 3174.83 2634.09 250(20)
 
a The vibrational modes are: ν33 (C3-C4 torsion), ν33 (C-C≡C bend), and ν31 (methyl internal rotation).

 

 

C5H8   -   Vinyl cyclopropane

Molecular constants for trans-vinyl cyclopropane
Species υ A [MHz] B [MHz] C [MHz] Ref.
t_CH(CHCH2)CH2_CH2 0 15262.(79) a 3061.368(19) 2941.132(18) b
1 15092.(150) 3071.43(5) 2944.02(5) 74063
2 14794.(150) 3081.38(5) 2946.70(5)
3 14875.(150) 3091.22(5) 2949.27(5)
t_CH(CHCH2)13CH2_CH2 0 15067. c 3022.66(10) 2896.45(10)
Electric Dipole Moment for t_CH(CHCH2)CH2_CH2
µa [C · m]
    µa [D]		 1.621(23) x 10-30
    0.486(7)		   74063
µc [C · m]
    µc [D]		 0.367(33) x 10-30
    0.110(10)
 
a The numbers in parentheses represent one standard deviation of the fit.
 
b J. Phys. Chem. Ref. Data 18(3), 1245-1524 (1989).
 
c Assumed value.

 

 

C5H8   -   Methylene cyclobutane

Molecular constants for methylene cyclobutane, CH2_CCH2CH2_CH2
Rotational Constants υ A [MHz] B [MHz] C [MHz] Ref.
Vibrational State a 0 10 373.9(16) 4618.05(6) 3459.87(5) 68044
1 10 368.8(16) 4592.21(6) 3462.95(5)
2 10 434.9(20) 4587.03(10) 3431.93(10)
3 10 358.9(20) 4603.81(10) 3460.43(10)
4 10 357.9(20) 4603.03(10) 3458.40(10)
5 10 308.6(20) 4613.34(10) 3475.42(10)
6 10 276.3(20) 4619.52(10) 3465.22(10)
Zeeman Constants υ=2 State
gaa -0.0320(8) µN 70063
gbb -0.0218(10) µN
g -0.0184(11) µN
2χaa - χbb - χcc -6.4(5) x 10-6 erg/(G2 · mol)
-χaa + 2χbb - χcc 4.3(17) x 10-6 erg/(G2 · mol)
Qaa -1.2(11) x 10-26 esu · cm2
Qbb -1.1(20) x 10-26 esu · cm2
Qcc 2.3(24) x 10-26 esu · cm2
 
a Ring puckering vibration.

 

 

C5H8   -   1-Methyl cyclobutene

Molecular constants for 1-methyl cyclobutene
Parameter CH3-C=_CHCH2_CH2

Ground State		 Ref. CH3-C=_CHCH2_CH2
Torsional
Excited State		 Ref.
A [MHz] 11 679.182(23) a 11 653.63 70069
B [MHz] 4219.51(10) 4214.93
C [MHz] 3292.015(8) 3290.19
ΔJ [kHz] 1.02(21)  
ΔJK [kHz] 3.49(65)
ΔK [kHz] -12.9(57)
δJ [kHz] 0.068(29)
δK [kHz] 3.73(87)
Internal Rotation Constants
Iα (u Å2) 3.16 b a 3.13 b 70069
λa 0.9945 0.9945
λb 0.1045 0.1045
θ 6.0° b  
s 43.63 44.33
F [GHz] 172.43 175.04
V3 (cm-1) 565.1(7) 583.(4)
V6 (cm-1)   -13.7(88)
Electric Dipole Moment
µa [C · m]
    µa [D]		 1.074(33) x 10-30
    0.322(10)		 70069  
µb [C · m]
    µb [D]		 0.520(40) x 10-30
    0.156(12)
 
a J. Phys. Chem. Ref. Data 18(3), 1245-1524 (1989). Note the units for ΔJ should be kHz as shown here.
 
b Asumed value.

Comments: Several errors in [70069]have been corrected. The 211-202 transition frequency should be 9395.59, and the A,E assignments of the 312-303 transition are reversed. The quantum numbers for the transition at 22 213.7 MHz should be 303 (not 203) and the line at 30 222. MHz should be 330 (not 303). The 524-515 E transition at 30 990.92 deviates by 1 MHz and was not fit.

 

 

C5H8   -   1-Dimethylallene

Molecular constants for 1-dimethylallene in the ground vibrational state
Parameter (CH3)2C=C=CH2 Ref.
à [MHz] 8263.990 82(298) 76060
B tilde [MHz] 3614.193 98(136)
C tilde [MHz] 2639.488 26(89)
ΔJ [MHz] 0.4970(95) x 10-3
ΔJK [MHz] 0.010 490(60) x 10-3
ΔK [MHz] 1.985(204) x 10-3
δJ [MHz] 0.157 23(173) x 10-3
δK [MHz] 6.108(40) x 10-3
Internal Rotational Constants
Iα (u Å2) 3.13 (assumed) 71050
θ 52.8°
s 56.66(6)
V3 (cm-1) 708.7(11)
Dipole Moment
µa [C · m]
    µa [D]		 1.831(3) x 10-30
    0.549(1)		 71050

 

 

Molecular constants for 1-dimethylallene in the ground vibrational state
State A [MHz] B [MHz] C [MHz] E (cm-1) Ref.
νI a 8259.16(20) 3617.640(20) 2640.214(20) ~191. 77040
νII a 8248.25(10) 3626.382(20) 2640.565(20) ~191.
ν16 8251.23(20) 3613.797(3) 2638.384(3) ~236.
ν32 8270.73(4) 3618.352(5) 2643.832(5) ~241.
2ν32 8274.1(25) 3622.60(9) 2648.28(1)  
ν11 8206.9(5) 3621.87(2) 2639.99(1) ~355.
 
a Coriolis perturbation analysis yields the constants D = 5989.38(40) MHz and ΔEII,I = 48761.2(10) MHz.

 

 

C5H8   -   1,3-Pentadiene

Molecular constants for trans- and cis-1,3-pentadiene
Parameter t-CH3CHCHCHCH2 c-CH3CHCHCHCH2 Ref.
A [MHz] 27 367.(872) 15 662.(62) a
B [MHz] 2160.616(4) 2658.391(17)
C [MHz] 2033.212(5) 2306.129(16)
ΔJ [kHz] 0.16(11) 0.51(26)
ΔJK [kHz]   -2.5(50)
Internal Rotational Constants
Iα (u Å2) 3.13 b 3.13 b
λa 0.9048 0.46 947
θ 25.2° b 62.0° b
V3 (cm-1) 624.0(21) 258.2(5)
S 44.19 20.55
F [GHz] 187.94 167.18
Electric Dipole Moment
µa [C · m]
    µa [D]		 1.871(7) x 10-30
    0.561(2)		 1.521(33) x 10-30
    0.465(10)		 70070
µb [C · m]
    µb [D]		 0.53(10) x 10-30
    0.16(3)		 0.617(50) x 10-30
    0.185(15)
 
a J. Phys. Chem. Ref. Data 18(3), 1245-1524 (1989).
 
a Assumed.

 

 

C5H8   -   Bicyclo[2.1.0]pentane

Molecular constants for bicyclo[2.1.0]pentane, _$CHCH2CH2_CH$CH2 a
Isotopic Species A [MHz] B [MHz] C [MHz] Ref.
Normal 9100.702(4) 6114.090(4) 4781.690(4) 72064
1-13C 8978.86(1) 6089.75(2) 4748.41(2)
2-13C 9003.32(2) 6035.70(2) 4708.81(1)
5-13C 9061.72(2) 5974.72(3) 4706.60(1)
1-d1 8583.42(1) 5975.33(2) 4657.34(6) 76052
2-endo-d1 8673.28(1) 5934.14(4) 4650.18(4)
2,3-exo-d2 8581.75(1) 5661.04(3) 4409.20(2)
2,3-endo-d2 8268.93(1) 5769.08(2) 4529.48(1)
5-exo-d1 9093.40(2) 5730.10(2) 4545.03(3)
5-endo-d1 8725.62(1) 5856.68(2) 4726.13(2)
Electric Dipole Moment
µa [C · m]
    µa [D]		 0.00(3) x 10-30
    0.00(1)		   72064
µc [C · m]
    µc [D]		 0.87(3) x 10-30
    0.26(1)
 
a Carbon atom 5 is bonded to atoms 1 and 4 of the 4-membered ring. Atom 1 and 4 and 3 and 3 are equivalent.

 

 

C5H8   -   3,3-Dimethylcyclopropene

Molecular constants for 3,3-dimethylcyclopropene
Parameter Value Ref.
A [MHz] 6872.964(73) a
B [MHz] 5353.250(11)
C [MHz] 3846.522(11)
µa [C · m]
    µa [D]		 0.957(10) x 10-30
    0.287(3)		 78029
 
a J. Phys. Chem. Ref. Data 18(3), 1245-1524 (1989).

 

 

C5H8   -   Cyclopentene

Molecular constants for cyclopentene in the ground state and excited out-of-plane bending state, _CHCHCH2CH2_CH2
Vibrational State υ A [MHz] B [MHz] C [MHz] µa [C · m]     µa [D] Ref.
Ground a 7298.53 7227.57 3948.78 0.634(20) x 10-30 0.190(6) 65035
1 a 7289.03 7228.50 3950.46 0.644(37) x 10-30 0.193(11)
2 7281.28 7202.98 3915.78  
3 7285.80 7218.36 3939.73
 
a These were fit together with the vibration rotation parameters δ01 = 1.34 x 105 MHz2/s2 and E1-E0 = 27 300 MHz.

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